Measuring the dynamic shear modulus of poroelastic foams in the audible frequency range

International audienceThe prediction of acoustical properties of multilayered systems including poroelastic layers using the full Biot theory is in principle possible but in practice limited by the absence of material data. One of the parameters that is difficult to measure is the dynamic rigidity of the porous frame. Current experimental methods are limited to the lower part of the audible frequency range 1 (typically below 400 Hz) and require special shapes of the sample (cube, cylindrical rod or very thin samples). Since most sound absorbing plastic foams are viscoelastic, the elastic moduli may vary strongly with frequency, a measuring technique in the full audible frequency range is needed. Recently 2 a new method for the measurement of the dynamic shear modulus of the frame of poroelastic foams in the medium and high audible frequency range (1 to 4 kHz) has been presented This method is based on the measurement of the velocity and the damping of a Rayleigh-type surface wave on sample with thickness larger than the Rayleigh wave penetration depth. The Rayleigh wave was excited through direct mechanical excitation of the frame or the porous material and detected using a laser-doppler vibrometer. The velocity of this wave is closely related to the shear velocity, which is directly linked to the shear modulus. The damping of the Rayleigh wave can be used to determine the imaginary part of the shear modulus.In this work a first attempt is made to measure the dynamic shear modulus on a layer of finite thickness. In this way there is no requirement whatsoever concerning the shape of the sample under investigation

Acoustical measurement of the shear modulus for thin porous layers

International audienceSimulations performed with the Biot theory show that for thin porous layers, a shear mode of the structure can be induced by a point-source in air located close to the layer. The simulations show that this mode is present around frequencies where the quarter wavelength of the shear Biot wave is equal to the thickness of the samples and show that it can be acoustically detected from the fast variations with frequency of the location of a pole of the reflection coefficient close to grazing incidence. The mode has been detected with this method for two reticulated plastic foams. For one of the foams studied, the velocity and the damping of the Rayleigh wave have been measured on a thicker layer of the same medium at higher frequencies, giving a real part of the shear modulus close to the one obtained from the measured location of the pole. The strong coupling of the shear mode with the acoustic field in air allows the measurement of the shear modulus without mechanical excitation

Guided elastic waves in porous materials saturated by air under Lamb conditions

International audienceThe propagation of guided elastic waves in porous materials saturated by air under Lamb conditions is studied theoretically and experimentally. The modes are derived from expressing the boundary conditions on the normal and tangential stresses and the displacements at the interfaces between the porous layer and the surrounding fluid. The stresses and the fluid pressure inside the porous medium are obtained from Biot's equations of poroelasticity. Symmetrical and antisymmetrical modes are found when the porous layer is loaded by the same fluid on both sides. Damping mechanisms include viscous and thermal exchanges between the solid and the fluid, in addition to the classical structural damping. Using an experimental setup based on the generation of standing waves in the layer and taking the spatial Fourier transform of the displacement profile, the phase velocities of three modes were measured for two porous materials in a frequency range between 80 Hz and 4 kHz. The measurements confirm the theoretical predictions and provide information on the shear modulus of a sound-absorbing material in a wide frequency range

Non-smooth contact dynamic approach for railway engineering: investigation of ballast behaviour under stabilisation process

Railway maintenance procedures include the stabilisation of ballasted tracks. The procedure of dynamic stabilisation which consists in vibrating laterally the rail while applying a vertical load is analysed using a discrete element code based on non-smooth contact dynamics. The ballast stones are modelled realistically using polyhedrons based on real ballast stones scans. The evolution of the compaction level and contact number between particles is analysed during the dynamic stabilisation process. A model is proposed to predict settlement. The results of simulation show the effectiveness of this maintenance procedure. It also points out the relevance of the model to predict settlement

Genome-wide analysis of the AP2/ERF superfamily in apple and transcriptional evidence of ERF involvement in scab pathogenesis

The APETALA2 (AP2)/ETHYLENE RESPONSE FACTOR (ERF) superfamily of transcriptional regulators is involved in several growth, development and stress responses processes in higher plants. Currently, the available information on the biological roles of AP2/ERF genes is derived from Arabidopsis thaliana. In the present work, we have investigated genomic and transcriptional aspects of AP2/ERF genes in the economically important perennial species, Malus ×domestica. We have identified 259 sequences containing at least one ERF domain in apple genome. The vast majority of the putative proteins display predicted nuclear localization, compatible with a biological role in transcription regulation. The AP2 and ERF families are greatly expanded in apple. Whole-genome analyses in other plant species have identified a single genomic sequence with divergent ERF, whereas in apple seven soloists are present. In the apple genome, the most noteworthy expansion occurred in sub-groups V, VIII and IX of the ERF family. Expression profiling analyses have revealed the association of ripening-involved ERF genes to scab (Venturia inequalis) pathogenesis in the susceptible Gala cultivar, indicating that gene expansion processes were accompanied by functional divergence. The presented analyses of AP2/ERF genes in apple provide evidences of shared ethylene-mediated signaling pathways in ripening and disease responses

ÉVALUATION DE LA SENSIBILITÉ AUX BIOAGRESSEURS DE 36 VARIÉTÉS DE POMMIERS DANS UN RÉSEAU DE PARCELLES BIOLOGIQUES À FAIBLES INTRANTS

Les bioagresseurs sont une des principales limites à la production de pomme dans les systèmes conduits en AB et à faibles niveaux d’intrants. Une des clefs du contrôle des bioagresseurs dans ces vergers est le choix des variétés (Trapman et Jansonius, 2008). La variabilité de l’expression de la sensibilité variétale peut être appréhendée grâce à un réseau multi-site pluri-annuel. Quatre parcelles de pommier biologique conduites de manière semi-extensive ont été plantées en 2002 afin d’identifier des variétés d’intérêts pour les systèmes à faible intrants. 36 variétés ont été suivies afin d’évaluer conjointement leur sensibilité à la tavelure, aux pucerons et à l’oïdium.La thématique de cette étude initiée en 2002 se trouve être au coeur des questionnements récents sur la réduction des intrants en arboriculture (programme ECOPHYTO 2018). Cette étude souligne (1) la spécificité des variétés intéressantes pour un site donné, (2) l’apparation dans certains cas de maladies considérées comme anecdoctiques, (3) l’intérêt de dispositifs multi-sites et d’observations pluriannuelles pour évaluer avec fiabilité la sensibilité aux bioagresseurs, (4) la méthodologie adaptée à cette problématique (méthode de notation, type de dispositif, etc)

Using whole-genome SNP data to reconstruct a large multi-generation pedigree in apple germplasm

Background Apple (Malus x domestica Borkh.) is one of the most important fruit tree crops of temperate areas, with great economic and cultural value. Apple cultivars can be maintained for centuries in plant collections through grafting, and some are thought to date as far back as Roman times. Molecular markers provide a means to reconstruct pedigrees and thus shed light on the recent history of migration and trade of biological materials. The objective of the present study was to identify relationships within a set of over 1400 mostly old apple cultivars using whole-genome SNP data (~253K SNPs) in order to reconstruct pedigrees. Results Using simple exclusion tests, based on counting the number of Mendelian errors, more than one thousand parent-offspring relations and 295 complete parent-offspring families were identified. Additionally, a grandparent couple was identified for the missing parental side of 26 parent-offspring pairings. Among the 407 parent-offspring relations without a second identified parent, 327 could be oriented because one of the individuals was an offspring in a complete family or by using historical data on parentage or date of recording. Parents of emblematic cultivars such as 'Ribston Pippin', 'White Transparent' and 'Braeburn' were identified. The overall pedigree combining all the identified relationships encompassed seven generations and revealed a major impact of two Renaissance cultivars of French and English origin, namely 'Reinette Franche' and 'Margil', and one North-Eastern Europe cultivar from the 1700s, 'Alexander'. On the contrary, several older cultivars, from the Middle Ages or the Roman times, had no, or only single, identifiable offspring in the set of studied accessions. Frequent crosses between cultivars originating from different European regions were identified, especially from the 19th century onwards. Conclusions The availability of over 1400 apple genotypes, previously filtered for genetic uniqueness and providing a broad representation of European germplasm, has been instrumental for the success of this large pedigree reconstruction. It enlightens the history of empirical selection and recent breeding of apple cultivars in Europe and provides insights to speed-up future breeding and selection

The mark of captivity: plastic responses in the ankle bone of a wild ungulate (Sus scrofa)

International audienceDeciphering the plastic (non-heritable) changes induced by human control over wild animals in the archaeological record is challenging. We hypothesized that changes in locomotor behaviour in a wild ungulate due to mobility control could be quantified in the bone anatomy. To test this, we experimented with the effect of mobility reduction on the skeleton of wild boar (Sus scrofa), using the calcaneus shape as a possible © 2020 The Authors. Published by the Royal Society under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/4.0/, which permits unrestricted use, provided the original author and source are credited. phenotypic marker. We first assessed differences in shape variation and covariation in captive-reared and wild-caught wild boars, taking into account differences in sex, body mass, available space for movement and muscle force. This plastic signal was then contrasted with the phenotypic changes induced by selective breeding in domestic pigs. We found that mobility reduction induces a plastic response beyond the shape variation of wild boars in their natural habitat, associated with a reduction in the range of locomotor behaviours and muscle loads. This plastic signal of captivity in the calcaneus shape differs from the main changes induced by selective breeding for larger muscle and earlier development that impacted the pigs' calcaneus shape in a much greater extent than the mobility reduction during the domestication process of their wild ancestors