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International audience; Description du sujet : Le changement climatique est un obstacle majeur pour la germination et la croissance précoce des semis, tout traitement biologique qui permet d’apporter une amélioration morpho-physiologique sera d’intérêt particulier.Objectifs : Notre objectif porte sur l’évaluation des potentialités de l’extrait aqueux d’Ulva rigida en tant qu’un agent de priming, et ses capacités à booster et stimuler les graines de blé sous différentes concentrations.Méthodes : La technique de priming a été réalisée sur les graines de blé en utilisant l’algue Ulva rigida comme agent. Après préparation de l’extrait aqueux, les graines ont été amorcées à différentes concentrations à raison 0,2 ml/250 ml, 0,3 ml/250 ml, 0,5 ml/250 ml et 1 ml/250 ml. L’eau de ville a été retenue comme témoin. L’essai a été réalisé pendant 10 jours. Les taux de germination et d’inhibition, l’indice et la vitesse de germination, poids frais, poids sec, longueur des parties aérienne et racinaire et l’accumulation des polyphénols totaux ont été estimés.Résultats : Les résultats ont indiqué l’efficacité de l’extrait aqueux d’Ulva rigida en tant qu’agent de priming. À la plus faible concentration (0,2 ml/250 ml), le taux de germination, l’indice et la vitesse de germination, la croissance racinaire et aérienne, ainsi que la teneur en polyphénols totaux ont été considérablement améliorées. Sous l’effet des concentrations 0,3 ml/250 ml et 0,5 ml//250 ml, le pouvoir stimulateur a enregistré une perte d’efficacité, accompagné d’une forte accumulation des polyphénols totaux. Enfin, la forte concentration, en l’occurrence 1 ml//250 ml, a exprimé un fort taux d’inhibition.Conclusion : L’extrait aqueux de l’algue verte Ulva rigida est un agent de priming prometteur, qui peut répondre aux attentes actuelles et futures des opérateurs économiques tout en assurant la pérennité de l'activité agricole. Aux fortes concentrations, il peut servir comme inhibiteur de la germination. En revanche, aux très faibles concentrations, il stimule la semence et performe le processus de germination même dans les situations de contraintes climatiques.

International audience; This study highlights, for the first time, the effect of Algerian nettle (Urtica dioïca L.) water extract against some phytopathogens bacteria. Results showed that water extract exhibited high level of total phenol content (261.7 ± 5.1 mg g−1 GAE) and a remarkable antioxidant activity (IC50 = 20.0 ± 0.6 µg mL−1) comparable to Trolox as reference (IC50 = 16.5 ± 0.5 µg mL−1). Moreover, results showed that water extract presented an interesting inhibition of some Gram-positive and Gram-negative phytopathogens’ bacteria. These results highlighted that secondary metabolites from Urtica dioïca could be an alternative pathway to synthetic pesticides for plant diseases control.

Essential oil is widely used in perfumery, cosmetic, pharmaceutic and food industries. The economics of essential oil production depend on both parameters; the cultivation of aromatic herbs and the extraction of oils from these herbs. This study investigated for the first time the variation in essential oil and composition of Cytisus triflorus L'Her plant at different growth times (vegetative, flowering and fruiting stages). Essential oil was extracted by hydro-distillation. The flowering stage show the highest essential oil yield (0.61 +/- 0.02 mL/100 g) compared to those of vegetative (0.41 +/- 0.01 mL/100 g) and fruiting (0. 17 +/- 0.01 mL/100 g) stages. For all growth stages, Thirty-eight compounds were identified, representing 93.21% - 95.47% of the oil, where the main components were beta-linalool (28.28 to 38.04%), Geraniol (19.82 to 27.73%), Retinal (4.33 to 9.26%), p-Mentha-1,4-dien-8-ol (2.09 to 4.08%), gamma-Terpinene (1.27 to 4.86%) and Eugenol (2.07 to 2.28%). Monoterpene hydrocarbons were detected at higher level at flowering compared to vegetative and fruiting stages. In contrast, aldehydes were noted at higher percentage at vegetative stage. This study highlighted difference in content and composition of essential oil in Cytisus triflorus L'Her during growth stages. Flowering was the interesting stage for harvesting and with more specific composition in essential oil.

International audience; Clustering data is an important topic in acoustic emission (AE) health monitoring. Identification of damage mechanisms in composites via AE technique requires an automatic process of classification. In this work, we propose a novel and simple supervised method to discriminate AE signals produced by fracture mechanisms in polymer composites. The novelty of this work is to propose new pertinent descriptors offered by using the continuous wavelet transform, where signals of learning are decomposed and the corresponding wavelet coefficients are calculated. In addition, the entropy criterion is applied to select the most correlated wavelets associated to each failure mechanism. This process allows to establish a filter in the form of vectors for each class of signals and descriptors denote the reconstruction errors calculated by involving the filter associated to each damage mechanism. The k-means algorithm is executed to calculate the center of each class. The technique is applied to AE signals recorded from specific mechanical tests to demonstrate the performance of the proposed descriptors.

International audience; Samples of pear shoots, blossoms and leaves showing typical fire blight symptoms were collected from diseased pear trees during spring and summer over a period of 3 years from orchards situated in the Mitidja region, a main pear producing area in Northern Algeria. From all collected plant samples, thirty-seven putative Erwinia amylovora strains were isolated and identified by biochemical, serological and molecular tests. Molecular typing of these strains was performed using six variable number of tandem repeats sequences (VNTRs). Minimal spanning trees showed that four different haplotypes were present within the bacterial population analyzed. The efficacy of twenty potential bacterial antagonists was evaluated in vitro against two E. amylovora pathogenic strains. Four antagonists (Bacillus amyloliquefaciens, Bacillus methylotrophicus and two Pseudomonas brassicaceaurum) were selected to perform a biocontrol assay on immature pear fruits. Results showed that the two Pseudomonas strains were the most effective for preventive treatment on pear fruits, leading to a necrosis reduction of up to 90%. No curative effect was observed. The four selected antagonists were characterized for features linked to biocontrol activity, such as biofilm, siderophores and biosurfactant-production, motility, and effect of environmental conditions on bacterial growth.

International audience; Natural diatomite from Sig/Algeria was treated with 0.5, 1.0, 3.0 and 5.0 M nitric acid solutions for 2 h under re flux at 333 K in order to improve its performance as support of catalyst. The purified silica powders obtained from frustules can also be used to reinforce composites. The solids obtained were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier transform infrared (FTIR) spectroscopy, thermal analyses, and nitrogen adsorption-desorption at 77 K. Treatment of diatomite earth with nitric acid reduced mineral impurities, such as Fe2O3 and alkali metal oxides (CaO, MgO), eliminated carbonates and increased SiO2 ratio from 88% to 98%. The SEM micrographs showed the original geometry of the pores to be preserved. The surface properties were also evaluated using inverse gas chromatography at infinite dilution (IGC-ID) and finite concentration (IGC-FC). The interest here was to establish whether the technique is sufficiently sensitive to detect variations in the surface properties of the diatomite due to this chemical treatment. The IGC analysis permitted to reach several surface energy components with organic probes. Between them, the distribution function of the adsorption energy sites obtained with the isopropanol probe revealed a silica structure after the 5 M nitric add treatment.

International audience; With recent advancements, micro-object contactless conveyers are becoming an essential part of the biomedical sector. They help avoid any infection and damage that can occur due to external contact. In this context, a smart micro-conveyor is devised. It is a Field Programmable Gate Array (FPGA)-based system that employs a smart surface for conveyance along with an OmniVision complementary metal-oxide-semiconductor (CMOS) HD camera for micro-object position detection and tracking. A specific FPGA-based hardware design and VHSIC (Very High Speed Integrated Circuit) Hardware Description Language (VHDL) implementation are realized. It is done without employing any Nios processor or System on a Programmable Chip (SOPC) builder based Central Processing Unit (CPU) core. It keeps the system efficient in terms of resource utilization and power consumption. The micro-object positioning status is captured with an embedded FPGA-based camera driver and it is communicated to the Image Processing, Decision Making and Command (IPDC) module. The IPDC is programmed in C++ and can run on a Personal Computer (PC) or on any appropriate embedded system. The IPDC decisions are sent back to the FPGA, which pilots the smart surface accordingly. In this way, an automated closed-loop system is employed to convey the micro-object towards a desired location. The devised system architecture and implementation principle is described. Its functionality is also verified. Results have confirmed the proper functionality of the developed system, along with its outperformance compared to other solutions.

International audience; his paper models and investigates the resonance frequency shift induced by the adsorption phenomena for an adatoms-nanobeam system including the small scale effect as well as rotary inertia and shear distortion effects. The Lennard-Jones (6–12) type potential is used to determine the adsorption-induced energy owing van der Waals (vdW) interaction mechanism between adatom-adatom and adatom-substrate. The small scale effect is introduced by using Eringen's nonlocal elasticity theory while the explicit expressions of inertia moment and shear force are derived from the standard Timoshenko beam equations in which the residual stress effect is accounted as an additive axial load. Numerical results showed that the resonance frequency shift is depended on each of the adsorption density, mode number and small scale effects. Thus, numerical results are discussed in detail for a proper analysis of dynamic vibration behavior of adatoms-nanobeam systems which are of interest in the development of mass sensing devices.

In this work, we are interested in the calculation of the probability of diffusion of slow ions (some Kev) by a solid surface, this calculation is based on the resolution of the Boltzmann equation in the transport theory. In this model valid for low scattering angles, the collisions are binary and the distribution of scattering centres in the target is homogeneous, this work is aimed at studying the effect of energy loss on the scattering probability of ions by a solid surface at low energy. We have described the projectile-target atom interaction by a screened Coulomb potential proposed by Ziegler - Birsack - Littmark potential (ZBL), We have considered the He+/ Si and He+/ Ni systems for different values ​​of the incident energy of the projectiles. Different values ​​of the scattering angle have been studied. In a first step, we calculated DP1, the probability of diffusion by neglecting the energy loss of the projectile in the target. However, for the large values ​​of the path in the target, the energy loss becomes important and therefore not negligible. . We have thus calculated the probability of diffusion DP2 by taking this effect into account. By calculating the relative correction made to the probability of diffusion, we have shown that it depends inversely on the incident energy and the angle of diffusion and proportionally on the atomic number of the target and distance travelled.; Nous nous intéressons dans ce travail au calcul de la probabilité de diffusion d'ions lents (quelques Kev) par une surface solide, ce calcul est basé sur la résolution de l'équation de Boltzmann dans la théorie de transport. Dans ce modèle valable pour les faibles angles de diffusion, les collisions sont binaires et la distribution des centres diffuseurs dans la cible est homogène, ce travail est pour but l'étude de l'effet de la perte d'énergie sur la probabilité de diffusion d'ions par une surface solide à basse énergie. Nous avons décrit l'interaction projectile-atome cible par un potentiel coulombien écranté proposé par Zigler - Birsack - Littmark potentiel (ZBL), Nous avons considéré les systèmes He+/Si et He+/Ni pour différentes valeurs de l'énergie incidente des projectiles .Différentes valeurs de l'angle de diffusion ont été étudiées. Dans une première étape, nous avons calculé AP, la probabilité de diffusion en négligeant la perte d'énergie du projectile dans la cible .Cependant, pour les grandes valeurs du parcours dans la cible, la perte d'énergie devient importante et donc non négligeable. Nous avons ainsi calculé la probabilité de diffusion AP2 en tenant compte de cet effet .En calculant la correction relative apportée à la probabilité de diffusion, nous avons montré qu'elle dépend inversement à l'énergie incidente et l'angle de diffusion et proportionnellement au numéro atomique de la cible et de distance parcourue.

International audience; This paper is concerned with the investigation of thermal loads and small scale effects on free dynamics vibration of slender simply-supported nanobeams perforated with periodic square holes network and subjected to temperature-induced loads. The Euler–Bernoulli beam model (EBM) and shear beam model (SBM) developed for the determination of resonance frequency are derived by modifying the standard Timoshenko beam equations. The small scale effect is included by using the Eringen's nonlocal elasticity theory while the thermal loads effect is included by considering the additional axial thermal force in the standard differential equations. Numerical results are shown that the resonance frequency change, the thermal loads and the small scale effects are depended on size and number of holes. Thus, numerical results are discussed in detail for a properly investigation of the dynamic behavior of perforated nanobeams which are of interest in the development of resonant devices integrated in micro/nanoelectromichanical systems (M(N)EMS).

International audience; This paper is concerned with the investigationof the shear effect on the dynamic behavior of a thinmicrocantilever beam with manufacturing process defects.Unlike the Rayleigh beam model (RBM), the Timoshenkobeam model (TBM) takes in consideration the shear effecton the resonance frequency. This effect become significantfor thin microcantilever beams with larger slendernessratios that are normally encountered in MEMS devicessuch as sensors. The TBM model is presented and analyzedby numerical simulation using Finite Element Method(FEM) to determine corrective factors for the correction ofthe effect of manufacturing process defects like the underetchingat the clamped end of the microbeam and the nonrectangularcross section of the area. A semi-analyticalapproach is proposed for the extraction of the Young’smodulus from 3D FEM simulation with COMSOL Multiphysicssoftware. This model was tested on measurementsof a thin chromium microcantilever beam of dimensions

This paper identifies and investigates the influence of technological defects of manufacturing process on the dynamic behavior of thin chromium microbeam. The analytical models will be analyzed and corrected using finite element method (FEM) to determine their validity under influence of technological defects. A semi-analytical model will be proposed for the extraction of corrective factors from 3D FEM simulation of dynamic behavior of microbeam. Final results indicate that the correction of technological defects is very significant for Cr microbeam 80x2x0.95μm3. In other hand, the corrected value of Young’s modulus is very close to the experimental results and it is about 279.1GPa.

International audience; La Modélisation par Eléments Finis Comme Outil Essentiel dans la Caractérisation des Structures MEMS : Application aux Microponts

National audience; Etude de Comportement Dynamique des Micropoutres MEMS : Simulation par FEM Sous COMSOL et ANSYS Multiphysiques

International audience; Le Traitement D'image Dans Les Mems : Outil Essentiel Dans La Caractérisation Sans Contacts Des Microsystèmes