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International audience; We establish general versions of the Ekeland variational principle (EVP), where we include two perturbation bifunctions to discuss and obtain better perturbations for obtaining three improved versions of the principle. Here, unlike the usual studies and applications of the EVP, which aim at exact minimizers via a limiting process, our versions provide good-enough approximate minimizers aiming at applications in particular situations. For the presentation of applications chosen in this paper, the underlying space is a partial quasi-metric one. To prove the aforementioned versions, we need a new proof technique. The novelties of the results are in both theoretical and application aspects. In particular, for applications, using our versions of the EVP together with new concepts of Ekeland points and stop and go dynamics, we study in detail human dynamics in terms of a psychological traveler problem, a typical model in behavioral sciences.

International audience; Background: - Nitrous oxide (N2O), as a potent greenhouse gas, is increasingly becoming a major multidisciplinary concern in recent years. Therefore, the removal of N2O using powerful green solvents such as ionic liquids (ILs) has turned into an attractive way to reduce the amount of N2O in the atmosphere. Methods: -The aim of this study was to establish rigorous models that can predict the solubility of N2O in various ILs. To achieve this, three advanced soft-computing methods, viz. cascaded forward neural network (CFNN), radial basis function neural network (RBFNN), and gene expression programming (GEP) were trained and tested using comprehensive experimental measurements. Significant Findings: - The obtained results demonstrated that the newly implemented models can predict the solubility of N2O in ILs with high accuracy. Besides, it was found that the CFNN model optimized using Levenberg-Marquardt (LM) algorithm was the best predictive paradigm (R2=0.9994 and RMSE=0.0047). Lastly, the Leverage technique was carried out, and the statistical validity of the newly implemented model was documented as more than 96% of data were located in the applicability realm of this paradigm.

International audience; In this article, we develop an extension of the Fourier transform solution method in order to solve conduction equation with nonperiodic boundary conditions (BC). The periodic Lippmann-Schwinger equation for porous materials is extended to the case of non-periodicity with relevant source terms on the boundary. The method is formulated in Fourier space based on the temperature as unknown, using the exact periodic Green function and form factors to describe the boundaries. Different types of BC: flux, temperature, mixed and combined with periodicity can be treated by the method. Numerical simulations show that the method does not encounter convergence issues due to the infinite contrast and yields accurate results for both local fields and effective conductivity.

International audience; An exopolysaccharide (EPS) was purified from the probiotic bacterium Bacillus licheniformis AG-06 isolated from the polyherbal fermented traditional medicine (Ashwagandharishta) of Indian Ayurveda. High-performance liquid chromatography (HPLC) based compositional analysis exhibits the heteropolymeric nature of the EPS consisting of galactose, rhamnose, xylose, mannose, and glucose, as the monomeric units. Fourier-transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopic analyses confirm the presence of typical carbohydrate polymer functional groups and structural units, respectively. The purified EPS demonstrates the web-like fibrous and porous nature in scanning electron microscopic and atomic force microscopic studies. The purified EPS had shown 71.83% and 67.79% of flocculation and emulsification activities, respectively. Antioxidant activity was evaluated against 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), nitric oxide, and superoxide free radicals and the scavenging actions were increased in a dose-dependent manner. Moreover, the purified EPS exhibits a significant cytotoxic activity against the human lung carcinoma cells (A549), which strongly suggests the anticancer potential of the EPS derived from B. licheniformis AG-06.

International audience; We analyze in this contribution the propagation of bulk and Rayleigh surface waves in periodic architectured materials undergoing internal damage. An elastic damageable continuum-based model is developed in the framework of the thermodynamics of irreversible processes, whereby the displacement experiences a jump across the faces of the propagating crack. The crack propagation involves an enhancement of the displacement field associated with embedded discontinuities, which remain localized within each (triangular type) finite element. The displacement discontinuity is regulated by the traction separation behavior described by an exponential cohesive model with damage hardening followed by softening. The effective mechanical properties of the overall network are evaluated versus the increasing damage. The phase velocities for the longitudinal and transverse modes are then computed continuously versus the amount of damage, considering successively the situations of symmetrically and unsymmetrically distributed damage occurrence and propagation. Simulation results show that although the crack pattern is different in these two situations, it has no impact on the evolution of the effective moduli versus global damage. The phase velocities computed based on the effective moduli decrease as damage propagates within the network; thus, it is an indicator of the amount of global damage.

International audience; Electrokinetic and electroosmotic couplings can play important roles in water and ions transport in charged porous media. Electroosmosis is the phenomena explaining the water movement in a porous medium subjected to an electrical field. In this work, a new model is obtained through a new up-scaling procedure, considering the porous medium as a bundle of tortuous capillaries of fractal nature. From the model, the expressions for the electroosmosis pressure coefficient, the relative electroosmosis pressure coefficient, the maximum back pressure, the maximum flow rate, the flow rate-applied back pressure relation and the product of the permeability and formation factor of porous media are also obtained. The sensitivity of the relative electroosmosis pressure coefficient is then analyzed and explained. The model predictions are then successfully compared with published datasets. Additionally, we deduce an expression for the relative streaming potential coefficient and then compare it with a previously published model and experimental data from a dolomite rock sample. We find a good agreement between those models and experimental data, opening up new perspectives to model electroosmotic phenomena in porous media saturated with various fluids.

In the paper, a new class of quasi-variational inequalities is introduced which can be applied in the study of Lur'e set-valued dynamical systems and game theory. An efficient method to solve the problem and the convergence analysis are provided.

International audience; Efforts to widen the scope of ionic liquids applications across diverse research areas have flourished in the last two decades with developments in understanding and tailoring their physical, chemical, and biological properties. The promising applications of ionic liquids-based materials as antimicrobial systems is due to their ability and flexibility to be tailored in varying sizes, morphologies, and surface charges. Ionic liquids are also considered as greener materials. Common methods for the preparation of ionic liquid-based materials include crosslinking, loading, grafting, and combination of ionic liquids with other polymeric materials. Recent research focuses on the tuning of the biological properties to design novel ionic liquids-based antimicrobial materials. Here, the properties, synthesis and applications of ionic liquids and ionic liquids-based materials are reviewed with focus on antimicrobial activities applied to water treatment, air filtration, food packaging, and anticorrosion.

International audience; In many industrial manufacturing processes, the ratio of the variance to the mean of a quantity of interest is an important characteristic to ensure the quality of the processes. This ratio is called the coefficient of variation (CV). A lot of control charts have been designed for monitoring the CV of univariate quantity in the literature. However, the CV control charts for multivariate quantity have not received much attention yet. In this paper, we investigate a variable sampling interval (VSI) Shewhart control chart for monitoring multivariate CV. The time between two consecutive samples is allowed to vary according to the previous value of the multivariate CV, which will help the chart to detect the process shifts faster. The comparison with the fixed sampling interval Shewhart chart is implemented to highlight the advantage of the VSI method. Finally, an illustrative example is demonstrated on real data.

International audience; Rammed earth (RE) is a construction material which is manufactured by compacting the soil within a formwork, in superimposed layers. RE is attracting scientific studies because of its sustainable properties : a very low embodied energy and an advantageous living comfort due to a particular benefic hygro-thermal behaviour. Numerous studies have been conducted to investigate RE material and RE structures, however, a lack of knowledge on the seismic performance of RE buildings is noticed. This paper presents an advanced numerical study to investigate the in-plane seismic behaviour of RE walls. First, a numerical model of an in-situ RE wall was constructed by using discrete element modelling (DEM). The relevancy of the numerical model was verified by comparing dynamic properties of the model with that measured on the in-situ wall. Then, a real earthquake excitation was applied to the model, in order to evaluate the seismic performance of the RE wall studied. This is the first time, to our knowledge, that a dynamic discrete explicite analysis was performed for a RE wall. The excitation was scaled at different amplitudes to assess the damages following different earthquake intensities. The results showed that for seismic excitations lower than 2.3 m/s2, RE walls studied had satisfying in-plane earthquake performance.

International audience; The realization of artificial photosynthesis in the photocatalytic CO2 transformation into valuable chemicals or solar fuels, such as CO, CH4 , HCOOH, and CH3OH, by solar-light harvesting is a promising solution to both global-warming and energy-supply issues. Recently, zinc oxide (ZnO) has emerged as an excellent oxidative photocatalyst among non-titanium metal oxides due to its availability, outstanding semiconducting and optical properties, non-toxicity, affordability, and ease of synthesis. However, ZnO wide bandgap and inability to absorb in the visible region has demanded particular modification for its practical use as a sustainable photocatalyst. This review provides a panorama of the latest advancement on ZnO photocatalysis for CO2 reduction with an overview of fundamental aspects. Various modification strategies such as transition metal and non-metal doping, loading of plasmonic metals, and surface vacancy engineering for tunning the properties and improving the performance of ZnO are elaborated. Composites or hetero-structuralization-based Z-scheme formation is also presented along with a detailed photocatalytic reduction mechanism. Moreover, a new novel Step-scheme (Sscheme) heterostructure modification with a charge transfer pathway mechanism is also highlighted. Finally, the key challenges and new directions in this field are proposed to provide a new vision for further improvement for ZnO-based photocatalytic CO2 conversion.

International audience; The authors regret that the name of the botanist who identified the plant material investigated was wrongly reported. The paragraph Plant Material should read as follows:“4.2. Plant material.Whole plants of Euphorbia tirucalli L. (Euphorbiaceae) were collected from Hong Son village, Ham Thuan Bac, in Binh Thuan province (11.129754° N, 108.143550° E) in July 2014 (wet season). The botanical sample was identified by Dr. Tran Cong Luan, Faculty of Pharmacy and Nursery, Tay Do University, Can Tho, Vietnam. A voucher specimen (No UP002) is deposited in the herbarium of the Department of Organic Chemistry, University of Science, Ho Chi Minh City.”

International audience; The Hill macrohomogeneity condition is revisited in the context of strain gradient homogenization for heterogeneous materials prone to interfacial displacement jumps. The consideration of strain gradient effects is motivated by their use as a regularization method for strain-softening constitutive damage models leading to strain localization and displacement discontinuity. Starting from the weak form of the boundary value problem formulated at the microscopic level, a polynomial expression of the virtual velocity is adopted as the minimum microscopic kinematics consistent with the selected macroscopic kinematics of the strain gradient effective continuum. The effective volumetric and interfacial mesoscopic strains and stress measures for the effective substitution are obtained versus the microscopic strains and stresses. The Hill macrohomogeneity condition is successively formulated for continuous interfaces and discontinuous interfaces witnessing strong discontinuities. It highlights the expressions of the effective stress measures associated to the volumetric and interfacial behavior for both classical and higher-order effects.

Based on the RILEM Technical Committee 274-TCE work, this paper is a discussion of the remaining engineering challenges faced by earthen architecture. The assessment of earth material performances requires the development of appropriate procedures and standards. This is discussed in particular for the characterisation, hygrothermal behaviour, mechanical behaviour, and durability of earth materials. One other important challenge, since one of the main advantages classically put forward, is its ecological performance, is a proper assessment of life cycle assessment of earth materials, elements and buildings. Moreover, the paper develops why the approach to earthen construction must be different compared to the dominant construction materials, to preserve its ability to contribute to the ecological transition in the construction sector. In particular, the needs of using local soils, with an architectural approach coping with the limits of the materials, and developing an architectural optimisation to preserve the earthen materials multifunctionality rather than selecting a sole property to be maximised. Lastly, the findings of the paper can be used to develop a holistic approach to earthen construction to foster the development of new earthen architecture projects.

The need for a vast quantity of new buildings to address the increase in population and living standards is opposed to the need for tackling global warming and the decline in biodiversity. To overcome this twofold challenge, there is a need to move towards a more circular economy by widely using a combination of alternative low-carbon construction materials, alternative technologies and practices. Soils or earth were widely used by builders before World War II, as a primary resource to manufacture materials and structures of vernacular architecture. Centuries of empirical practices have led to a variety of techniques to implement earth, known as rammed earth, cob and adobe masonry among others. Earth refers to local soil with a variable composition but at least containing a small percentage of clay that would simply solidify by drying without any baking. This paper discusses why and how earth naturally embeds high-tech properties for sustainable construction. Then the potential of earth to contribute to addressing the global challenge of modern architecture and the need to re-think building practices is also explored. The current obstacles against the development of earthen architecture are examined through a survey of current earth building practitioners in Western Europe. A literature review revealed that, surprisingly, only technical barriers are being addressed by the scientific community; two-thirds of the actual barriers identified by the interviewees are not within the technical field and are almost entirely neglected in the scientific literature, which may explain why earthen architecture is still a niche market despite embodying all the attributes of the best construction material to tackle the current climate and economic crisis. This article is part of the theme issue ‘The role of soils in delivering Nature's Contributions to People’.

International audience; The homogenization of viscoelastic composite materials gives rise to long-memory effects, reflected by the presence in the homogenized viscoelastic constitutive law of a delayed stress response expressed as a convolution integral involving the past material strain history. Computations reveal that the long-memory has the ability to delay or even absorb waves depending on the fraction of reinforcement and relative properties of the building phases with the composite. An approximation by a one-term Prony series of the computed spectrum of retardation times is shown to provide an accurate representation of the continuous spectrum of retardation times when simulating creep experiments. The long-memory effects entail shifts of the frequency band diagrams for both the natural and damped frequencies due to the presence of damping. Decreasing the effective retardation time of the composite leads to a faster attenuation of propagating longitudinal and shear waves.

International audience; This paper proposed an efficient model predictive control strategy for a three-level T-type inverter connected to a doubly fed induction generator. A dynamic model is utilized to track the power reference, preserve the DC-link voltage balancing and reduce the inverter switching frequency and common-mode voltage. Unlike the traditional finite control set model predictive control, the stability of the closed-loop system and computational burden reduction are concurrently accomplished as the main contribution to the proposed strategy. At each sampling period, the proposed algorithm only considers the candidate control inputs which satisfy the stability condition taken from a suitable control Lyapunov function for evaluating the optimization problem. Due to model uncertainties and discrete set control input voltages, an attractivity set is employed to determine the stability and converge of the system. Therefore, the lower computation time of the optimization problem is the potential benefit compared with the conventional method. Simulation investigation with different operating conditions of a 2 MW wind turbine is carried out by MATLAB/Simulink. The achieved results confirm the stability guarantees while reducing the computational burden and obtaining the same control performances in comparison with the conventional method.

Natural convection in cavities is an interesting subject for many researchers. Especially, in recent years, the number of articles written in this regard has grown enormously. This work provides a review of recent natural convection studies. At first, experimental studies were reviewed and, then, numerical studies were examined. Then, the articles were classified based on effective parameters. In each section, numerical studies were examined the parameters added to the cavity such as magnetic forces, fin, porous media and cavity angles. Moreover, studies on non-rectangular cavities were investigated. Free convection in enclosures depends more on the fluid velocity relative to the forced convection, leading to the opposite effect of some parameters that should essentially enhance rate of heat transfer. Nanoparticle addition, magnetic fields, fins, and porous media may increase forced convection. However, they can reduce free convection due to the reduction in fluid velocity. Thus, these parameters need more precision and sometimes need the optimization of effective parameters.

This research investigated artificial neural network (ANN) modeling to predict the exhaust emissions and engine performance. Different percentages of alcohol at various engine speeds and comparison ratios were used to obtain the required data for testing and training the proposed ANN. Six experimental datasets were used for the training process to develop an ANN model based on the standard program. Furthermore, the accuracy of the proposed model was evaluated by calculating the mean square error (MSE), regression coefficient (R2), and average absolute relative deviation (AARD%). The total values of AARD% for the proposed model were 10.50 and 15.45% for carbon monoxide and hydrocarbon emissions and 10.50 and 3.13% for torque and fuel consumption, respectively, which were acceptable errors compared with the experimental uncertainty.

Neurodegenerative diseases are usually characterized by plaques made of well-ordered aggregates of distinct amyloid proteins. Dissociating these very stable amyloid plaques is a critical clinical issue. In this study, we present a joint mid-infrared free electron laser experiment/nonequilibrium molecular dynamics simulation to understand the dissociation process of a representative example GNNQQNY fibril. By tuning the laser frequency to the amide I band of the fibril, the resonance takes place and dissociation is occurred. With the calculated and observed wide-angle X-ray scattering profiles and secondary structures before and after laser irradiation being identical, we can propose a dissociation mechanism with high confidence from our simulations. We find that dissociation starts in the core of the fibrils by fragmenting the intermolecular hydrogen bonds and separating the peptides and then propagates to the fibril extremities leading to the formation of unstructured expanded oligomers. We suggest that this should be a generic mechanism of the laser-induced dissociation of amyloid fibrils.

International audience; The aggregation of the amyloid (Aβ) peptide of 39−43 amino acids into plaques is observed in the brain of Alzheimer's disease (AD) patients, but the mechanisms underlying the neurotoxicity of Aβ oligomers are still elusive. One suggested initial mechanism is related to the implications of amyloid membrane interactions, but characterization of these assemblies is challenging by experimental means. In this study, we have explored the stability of a trimer of Aβ11−40 in parallel and antiparallel β-sheet structures for the wild-type sequence and its F20W mutant in a dipalmitoylphosphatidylcholine membrane using atomistic replica exchange molecular dynamic simulations. We show that both the U-shape organization and the assembly of β-hairpins are maintained in the membrane and are resistant to the mutation F20W. In contrast the models are destabilized by the F19P mutation. Overall, our results indicate that these two assemblies represent minimal seeds or nuclei for the formation of either amyloid fibrils, a variety of β-barrel pores, or various aggregates for many Aβ sequences in a membrane-mimicking environment.

Skin cancer is one of the most common cancers in the world. However, the disease is curable if detected in the beginning stage. Early detection of malignant lesions through accurate techniques and innovative technologies has a significant impact on reducing skin cancer mortality rates. Recently, artificial intelligence has come to the forefront to facilitate skin cancer diagnosis based on medical images. Many deep learning models have been studied and developed, but the imbalance of performance among classes in the multi-class classification is still a challenging problem. This study proposes a hybrid method for handling class imbalance of skin-disease classification. This method combines the data level method of balanced mini-batch logic followed by real-time image augmentation with the algorithm level method of designing new loss function. The training dataset includes 24,530 dermoscopic images of seven skin disease categories, which is by far the largest dataset of skin cancer. The performance metrics of six proposed methods are evaluated on a test dataset of 2,453 images. Our proposed EfficientNetB4-CLF model achieves the highest accuracy of 89.97% and also the highest mean recall of 86.13% with the smallest recalls' standard deviations of 7.60%. Compared to the original methods, our proposed solution not only surpasses 4.65% (86.13% vs 81.48%) of mean recalls but also reduces 4.24% of the recalls' standard deviations (from ±11.84% to ±7.60%). This result indicates that our hybrid method is highly effective in training the Deep CNN network on the skin-disease imbalanced dataset. It addresses the problem of slow learning of the minority classes in the networks by combining the data level method of balanced mini-batch logic followed by the real-time image augmentation with the algorithm level method of the newly designed loss function.

Estimating the solubility of carbon dioxide in ionic liquids, using reliable models, is of paramount importance from both environmental and economic points of view. In this regard, the current research aims at evaluating the performance of two data-driven techniques, namely multilayer perceptron (MLP) and gene expression programming (GEP), for predicting the solubility of carbon dioxide (CO2) in ionic liquids (ILs) as the function of pressure, temperature, and four thermodynamical parameters of the ionic liquid. To develop the above techniques, 744 experimental data points derived from the literature including 13 ILs were used (80% of the points for training and 20% for validation). Two backpropagation-based methods, namely Levenberg−Marquardt (LM) and Bayesian Regularization (BR), were applied to optimize the MLP algorithm. Various statistical and graphical assessments were applied to check the credibility of the developed techniques. The results were then compared with those calculated using Peng−Robinson (PR) or Soave−Redlich−Kwong (SRK) equations of state (EoS). The highest coefficient of determination (R2 = 0.9965) and the lowest root mean square error (RMSE = 0.0116) were recorded for the MLP-LMA model on the full dataset (with a negligible difference to the MLP-BR model). The comparison of results from this model with the vastly applied thermodynamic equation of state models revealed slightly better performance, but the EoS approaches also performed well with R2 from 0.984 up to 0.996. Lastly, the newly established correlation based on the GEP model exhibited very satisfactory results with overall values of R2 = 0.9896 and RMSE = 0.0201.

It is commonly accepted that nanoparticles can kill bacteria; however, the mechanism of antimicrobial action remains obscure for nanoparticles that are unable to be translocated across the bacterial cell membrane by the passive or active processes that exist for mammalian cells. In this study, we demonstrate that the increase of membrane tension provoked by the adsorption of nanoparticles (NP) is responsible for mechanical deformation of the membrane that leads to cell rupture and consequent bacterial cell death. We present a biophysical model of the NP- membrane interactions. The theoretical model suggests that adsorbed NPs can lead to global stretching and squeezing of the membrane. This general phenomenon was revealed experimentally using both model membranes and bacterial cells. Hydrophilic and hydrophobic quasi-spherical and star shaped gold (Au)NPs were synthesised to explore the antibacterial mechanism of non-translocating AuNPs in vitro. Direct observation of nanoparticle-induced membrane tension and squeezing was realised by a custom-designed microfluidic device that revealed the contraction of the model membrane surface area that resulted in the eventual collapse of the lipid bilayer. Quasi-spherical nanoparticles exhibited a greater bactericidal action due to a higher interactive affinity that resulted in higher degrees of membrane stretching and rupturing, as confirmed by the theoretical model. Electron microscopy techniques were used to characterise the nanoparticle-bacterial-membrane interactions. This combination of experimental and theoretical results confirmed the proposed mechanism of membrane-tension-induced (mechanical) killing of bacterial cells by non-translocating NPs.

International audience; It is commonly accepted that nanoparticles (NPs) can kill bacteria; however, the mechanism of antimicrobial action remains obscure for large NPs that cannot translocate the bacterial cell wall. It is demonstrated that the increase in membrane tension caused by the adsorption of NPs is responsible for mechanical deformation, leading to cell rupture and death. A biophysical model of the NP-membrane interactions is presented which suggests that adsorbed NPs cause membrane stretching and squeezing. This general phenomenon is demonstrated experimentally using both model membranes and Pseudomonas aeruginosa and Staphylococcus aureus, representing Gram-positive and Gram-negative bacteria. Hydrophilic and hydrophobic quasi-spherical and star-shaped gold (Au)NPs are synthesized to explore the antibacterial mechanism of non-translocating AuNPs. Direct observation of nanoparticle-induced membrane tension and squeezing is demonstrated using a custom-designed microfluidic device, which relieves contraction of the model membrane surface area and eventual lipid bilayer collapse. Quasi-spherical nanoparticles exhibit a greater bactericidal action due to a higher interactive affinity, resulting in greater membrane stretching and rupturing, corroborating the theoretical model. Electron microscopy techniques are used to characterize the NP-bacterial-membrane interactions. This combination of experimental and theoretical results confirm the proposed mechanism of membrane-tension-induced (mechanical) killing of bacterial cells by non-translocating NPs.

International audience; In this study, we have investigated the use of silver cation as nucleating agent in germanotellurite glass matrix of compositions (100−x) [70TeO2–10GeO2–10Nb2O5–10K2O]–xAg2O (x=0-6 mol%), in order to promote bulk crystallization. Density measurements, differential scanning calorimetry, X-ray diffraction, UV-Vis, and Raman spectroscopies have been performed to study the crystallization process. We have observed bulk crystallization of a unique noncentrosymmetric phase, K[Nb1/3Te2/3]2O4.8, which has been investigated for its second-order optical activity. Transparent to translucent glass-ceramics have been successfully tailored under thermal treatment and second harmonic generation signals were recorded on the glass-ceramic samples as a function of their synthesis procedure. It is suggested that the second-order optical properties observed are strongly related to the organization of crystallites within phase-separated domains.

International audience; Evaluations of the functioning of benthic marine food webs could be improved by quantifying organic matter fluxes from the meiofauna to higher trophic levels. In this study, we measured the simultaneous ingestion of meiofauna and macrofauna by common dwellers of a tropical intertidal mudflat on the coast of Amazonia. The meiofauna and macrofauna (tanaid) communities of a tropical intertidal mudflat of French Guiana were separately enriched with 15N and 13C, respectively. The enriched preys were then used as tracers during feeding experiments with common predators of different sizes and feeding mechanisms: a Portunidae crab (Callinectes bocourti), a Penaeidae shrimp (Farfantepenaeus subtilis) and a Gobiidae fish (Gobionellus oceanicus). In feeding experiments with all predators except crabs, feeding rates increased with the availability of meiofauna and macrofauna food sources. The ability of consumers to ingest their food selectively was evaluated by calculating the differences in the ratio of macrofauna to meiofauna between the i) ingested material and ii) that available in the environment. Larger predators showed a higher degree of preferential macrofauna ingestion than smaller predators, consistent with the optimal foraging theory. For large predators, the meiofauna would be important only during early life or in the absence of large food items.

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International audience; A simple and accurate model for predicting the elastic properties of gas hydrate-bearing sediment (GHBS) is proposed and validated against experimental data. It is developed on the basis of the homogenization theory for multiphase composite. Unlike the classical homogenization techniques those fix a homogenization scheme (e.g. self-consistent, Mori-Tanaka, DEM, etc.) for a given microstructure, the proposed model considers a flexible homogenization scheme that adapts with the change of the microstructure of the material. The idea is to modify the elastic properties of the reference matrix with respect to the microstructure change of the mixture. Such modification is ensured by adapting the theoretical method to available experimental data. The derived method is proved to be very powerful as it can fit laboratory measured data on gas hydrate-bearing sand formed by different methods including excess gas and excess water methods and log data taken from various sites. Such feature cannot be satisfied by the existent models those consider the hydrate phase as a cement phase or a pore-filling phase. A very good agreement between the proposed method and experimental data offer a simple and accurate ways to predict the saturation of gas hydrate using sonic log data or 3D seismic data.

We investigate whether there are racial and ethnic disparities in children's education in Ethiopia, India, Peru and Viet Nam. We find that in all the four countries, and especially in Viet Nam, children from small ethnic groups have lower education attainment and cognitive ability. The gap in educational attainment and cognitive ability among ethnic children is larger than the gap in school enrolment, and the gap tends to be wider for older children. Using the Oaxaca-Blinder decomposition, we find that the main contribution to the gap in education between children from small ethnic groups and large ethnic groups in India, Peru and Viet Nam is the difference in endowments (i.e., characteristics of children and their families) rather than the difference in the coefficients of endowments. However, in Ethiopia, the difference in the coefficients contributes more than the difference in endowments to the gap in education. Child health, parental education, household expenditure and an urban environment are important variables for explaining the gap in education between children from small and large ethnic groups.

International audience; Time-dependend evolution of hydrodynamic turbulence corresponding to formation of a thermodynamic state at the large-scale part of the spectrum is studied using the inviscid Leith model. In the wave vector space, the evolution leads to shrinking of the zero-spectrum "hole"-the so-called focusing problem. However, in contrast with the typical focusing problem in the nonlinear filtration theory, the focusing time is infinite for the Leith model. Respectively, the evolution is described by a self-similar solution of the third kind (discovered in Nazarenko, Grebenev [Phys A: Math. Theor. 50, 3, 2017]), and not the second kind as in the case of the typical filtration problem. Using a phase-plane analysis applied to the dynamical system generated by this type of similarity, we prove the existence of a new self-similar spectrum to this problem. We show that the final stationary spectrum scales as the thermodynamic energy equipartition spectrum, E ∼ k 2 .

The omega-3 and omega-6 polyunsaturated fatty acids are two important components of cell membranes in human brains. When incorporated into phospholipids, omega-3 slows the progression of Alzheimer's disease (AD), whereas omega-6 is linked to increased risk of AD. Little is known on the amyloid-β (Aβ) conformations in membranes rich in omega-3 and omega-6 phospholipids. Herein, the structural properties of the Aβ29-42 dimer embedded in both fatty acid membranes were comparatively studied to a 1-palmitoyl-2-oleoyl- sn-glycero-3-phosphocholine (POPC) bilayer using all-atom molecular dynamics (MD) simulations. Starting from α-helix, both omega-6 and omega-3 membranes promote new orientations and conformations of the dimer, in agreement with the observed dependence of Aβ production upon addition of these two fatty acids. This conformational result is corroborated by atomistic MD simulations of the dimer of the 99 amino acid C-terminal fragment of amyloid precursor protein spanning the residues 15-55. Starting from β-sheet, omega-6 membrane promotes helical and disordered structures of Aβ29-42 dimer, whereas omega-3 membrane preserves the β-sheet structures differing however from those observed in POPC. Remarkably, the mixture of the two fatty acids and POPC depicts another conformational ensemble of the Aβ29-42 dimer. This finding demonstrates that variation in the abundance of the molecular phospholipids, which changes with age, modulates membrane-embedded Aβ oligomerization.

International audience; Rammed earth (RE) is a construction material which is made by compacting the soil in a formwork. This material is attracting the attention of the scientific community due to its sustainable characteristics. Among different aspects to be investigated, the seismic performance remains an important topic which needs advanced investigations. The existing studies in the literature have mainly adopted simplified approaches to investigate the seismic performance of RE structures. The present paper adopts a numerical approach to investigate the seismic behavior of RE walls with an L-form cross-section. The 3D FEM model used can take into account the plasticity and damage of RE layers and the interfaces. The model was first validated by an experimental test presented in the literature. Then, the model was employed to assess the seismic performance of a L-form wall of a RE house at different amplitudes of earthquake excitations. Influences of the cross-section form on the earthquake performance of RE walls were also investigated. The results show that the L-form cross-section wall has a better seismic performance than a simple rectangular cross-section wall with similar dimensions. For the L-form cross-section wall, the damage observed concentrates essentially on the connection between two flanges of the wall.

International audience; The phytochemical investigation of Euphorbia tirucalli L. (Euphorbiaceae) yielded four new compounds, including a rare cadalene-type sesquiterpene (tirucadalenone), two tirucallane triterpenoids, euphorol L and euphorol M, with the latter being described as an epimeric mixture, and a euphane triterpene, namely, euphorol N, together with 7 known compounds. Their structures and absolute configurations were elucidated from analysis of 1D (1H, J-modulated C) and 2D NMR (HSQC, HMBC and NOESY), high-resolution mass spectrometry (HRESIMS), optical rotation, and GIAO NMR shift calculation followed by CP3 analysis, along with comparison with literature reports. All these compounds were tested for cytotoxicity against K562, MCF-7 and/or and HepG2 tumor cell lines. Only tirucadalenone displayed a mild cytotoxic activity.

International audience; Nano-fluidic flow and heat transfer around a horizontal cylinder at Reynolds numbers up to 250 are investigated by using weakly compressible smoothed particle hydrodynamics (WCSPH). To be able to simulate enhanced nanoparticle heat transfer, this manuscript describes for the first time a development that allows conductive and convective heat transfer to be modelled accurately for the Eckert problem using WCSPH. The simulations have been conducted for Pr = 0.01–40 with nanoparticle volumetric concentrations ranging from 0 to 4%. The velocity fields and the Nusselt profiles from the present simulations are in a good agreement with the experimental measurements. The results show that WCSPH is appropriate method for such numerical modelling. Additionally, the results of heat transfer characteristics of nano-fluid flow over a cylinder marked improvements comparing with the base fluids. This improvement is more evident in flows with higher Reynolds numbers and higher particle volume concentration.

A phytochemical investigation of the foliose lichen Parmotrema tsavoense (Krog and Swinscow) Krog and Swinscow (Parmeliaceae) resulted in the isolation of a new trichlorinated xanthone, isodemethylchodatin. The structure elucidation of this new norlichexanthone derivative proved tricky owing to proton deficiency, and to the lack of NMR data of closely related analogues. The structure of this compound was determined based on an integrated interpretation of 13C-NMR chemical shifts, MS spectra, and DP4-based computational chemistry was also performed to provide an independent and unambiguous validation of the determined structure. Isodemethylchodatin represents the first chlorinated lichexanthone/norlichexanthone derivative bearing a methoxy group at C-5.

In this study, a new series of assessments and evaluations of the Dual-Miller cycle is performed. Furthermore, the specified output power and the thermal performance associated with the engine are determined. Besides, multi-objective optimization of thermal efficiency, ecological coefficient of performance (ECOP) and ecological function ( E u n ) by means of NSGA-II technique and thermodynamic analysis are presented. The Pareto optimal frontier obtaining the best optimum solution is identified by fuzzy Bellman-Zadeh, Linear Programming Technique for Multidimensional Analysis of Preference (LINMAP), and Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) decision-making techniques. Based on the results, performances of dual-Miller cycles and their optimization are improved. For the results of the condition that (n < k) the best point has been LINMAP answer. The thermal efficiency for this point has been 0.5388. In addition, ECOP and E u n have been 1.6899 and 279.221, respectively. For the results of the condition that (n > k) the best point has been LINMAP and TOPSIS answer. The thermal efficiency for this point has been 0.5385. Also, ECOP and E u n have been 1.6875 and 279.7315, respectively. Furthermore, the errors are examined through comparison of the average and maximum errors of the two scenarios.

Changes in the mechanical properties of granular materials, induced by variations in the intrinsic compressibility of the particles, are investigated by means of numerical simulations based on the combination of the Finite Element and Contact Dynamics methods. Assemblies of athermal 2D particles are subjected to quasi-static uni-axial compactions up to packing fractions close to $1$. Inspired by the contact mechanics in the Hertz's limit, we show that the effect of the compressibility of the particles both on the global and the local stresses, can be described by considering only the packing fraction of the system. This result, demonstrated in the whole range of accessible packing fractions in case of frictionless particles, remains relevant for moderate inter-particles coefficients of friction. The small discrepancies observed with frictional particles originate from irreversible local reorganizations in the system, the later being facilitated by the compressibility of the particles.

In this paper, forced convection of a multiwalled carbon nanotube (MWCNT)&ndash, water nanofluid (NF) in a new flat plate solar collector (FPSC) equipped with elliptical pipes instead of circular ones is investigated. The three-dimensional conservation equations were solved in the domain with the finite volume method (FVM) based on the semi-implicit method for pressure linked equations (SIMPLE) algorithm. The laminar-turbulent range of the Reynolds number (Re) and the volume fraction of the NF (ϕ) were 50&ndash, 12,000 and 0&ndash, 0.1, respectively. The optimization process was accomplished through the comparison of diverse parameters to attain the optimal case with the highest exergy efficiency. In this study, it was concluded that, in the case of using elliptical pipes instead of circular tubes, the time that the fluid was inside the FPSC increased, which led to an increase in the outlet temperature, while the exergy efficiency of the FPSC increased. Additionally, it was observed that using elliptical pipes enhanced the outlet fluid temperature, energy efficiency, and exergy efficiency. Generally, while the trend of exergy efficiency variation with effective parameters was rising, applying elliptical pipes caused the efficiency to increase. In addition, the exergy efficiency variation decreased when these parameters were changed. The highest value of exergy efficiency was 7.1%. On the other hand, for each specific FPSC, there was a unique mass flow rate at which the exergy efficiency reached its maximum value, and for higher mass flow rates, the efficiency was slightly diminished and then remained unchanged. Finally, the highest exergy efficiency was achieved for ϕ = 0.10%.

Horse chestnut, Aesculus hippocastanum L. (Sapindaceae), is a large deciduous tree native to a small area in the Pindus Mountain mixed forests and the Balkan mixed forests of Southeast Europe. It was introduced to most countries in Europe mainly for ornamental purposes. The aim of the present study was to assess the occurrence, species composition and population densities of phytoseiid mites on A. hippocastanum in countries where this tree species is autochthonous and to compare them with Central Europe. In addition, we tested whether the horse chestnut leaf miner, Cameraria ohridella or the horse chestnut leaf blotch, Guignardia aesculi has any effect on Phytoseiidae population density. Leaf samples were collected in the cities of České Budějovice, Czech Republic and Orestiada, Greece in September 2013 and 2015, respectively. Thirty compound leaves were randomly taken from tree branches up to 2.5 m above ground in both localities. Mites were collected by washing the leaves in ethanol and were then mounted in lactic acid and identified. A total of 441 specimens of phytoseiid mites belonging to six species (Euseius finlandicus, Neoseiulella tiliarum, Kampimodromus aberrans, Paraseiulus talbii, Phytoseius macropilis and Typhlodromus (Typhlodromus) pyri) were collected. A significantly higher population density of Phytoseiidae was found in České Budějovice. The density was not affected by the horse chestnut leaf miner, Cameraria ohridella or the horse chestnut leaf blotch, Guignardia aesculi. Euseius finlandicus was the predominant species in both České Budějovice (96.8%) and Orestiada (48.4%) where, however, it competed with K. aberrans (42.9%)., Acarologia, 58, 83-90

International audience; A new concept for the soil nail walls is here proposed and validated through experimental and numerical approaches. This process, based on the use of precast elements that are easier to install, is cheaper and more aesthetic than the classical methods, but the main advantage is reducing the cement consumption which conducts to divided carbon footprint by three. In order to characterize the structural capacity of this new process, this article present an investigation on two in-situ representative walls, one in shotcrete which is the old way of construction, and the other, consisting the precast reinforced concrete slabs, which is the new process. We thus have a demonstrator on a real scale, and perfectly representative, since the constructive modes, as well as the mechanical, thermal, and hydric loadings are the real ones associated with the environment in situ. Substantial instrumentation has been realized over a long period (nearly 2 years), enabling to follow the evolution of the displacements of each wall and the efforts in the anchor nails. To determine the bearing capacity of the constituent element of the precast nail wall, an experimental study coupled with a numerical simulation has been conducted in the laboratory on a single precast slab. This study allows the evaluation of the load associated to crack initiation and the bearing capacity associated to the ultimate state, at the scale of the constituent elements. Finally, in order to evaluate the behaviour of the two concepts of nail walls in the case of extreme solicitation, a dynamic loading induced by an explosion has been conducted on the site.

Beam-column joints are critical regions for reinforced concrete (RC) frames subjected to earthquakes. The steel reinforcement is, in general, highly concentrated in these zones. This is why in many cases, headed bars are used. A headed bar is a longitudinal steel reinforcement whose end has a special button added to reduce the bonding length of the steel rebar. This paper establishes a formula predicting the shear strength of exterior RC beam-column connections where the beam longitudinal reinforcements use headed bars. A database was collected, which contained 30 experimental data about the exterior beam-column joints using headed bars and subjected to quasi-static cyclic loading. First, from the collected database, a statistical study was carried out to identify the most influencing parameters on the shear strength of the beam-column joints tested. The three most important parameters were identified and an empirical modified formula was developed based on the formula existing in the standards. The study showed that the results obtained from the modified formula proposed in the present study were closer to the experimental results than that obtained from the formula existing in the standards. Finally, a numerical study was performed on two T-form RC structures and the numerical results were compared with the prediction calculated from the modified formula proposed. For two investigated cases, the proposed formula provided the results in the safety side and the differences with the numerical results were less than 20%. Thus, the proposed formula can be used for a rapid assessment of the shear strength of RC joints using headed bars.

cited By 24; The new nanocomposite material of CuFe2O4 (copper ferrite) nanoparticles coated by SiO2 is synthesized. Then, this newly generated nanocomposite is dispersed in water/ethylene glycol (60:40) to make a new homogeneous nanofluid in order to avoid settling and agglomeration. Through suitable accurate experiments, density, viscosity and electrical conductivity of the mixture are measured at various temperatures and nanoparticles concentrations. Besides we empirical correlations for the same parameters developed via the curve fitting method. To have a better statistical view, the optimization procedure based on the enhanced artificial neural network (EANN), developed at present study, is performed. Furthermore, according to the obtained empirical results, the sensitivity analysis is provided and the margin of deviations is represented for each proposed correlation. Generation, stabilization and measuring the density, viscosity and electrical conductivity of the newly mentioned nanofluid, make present work different from the previous ones in this field. The highest amount of relative electrical conductivity is observed at T = 75 °C and φ = 0.02 (g/mL); however, the case of T = 30 °C and φ = 0.02 (g/mL) represents the maximum value of relative viscosity. Moreover, density is decreased by temperature augmentation, through all cases. © 2018 Elsevier Ltd

International audience; New racemic dispiranic polyketides, tsavoenones A (1), B (2) and C (3), having a novel 1,7-dioxadispiro[4.0.4.4]tetradecane scaffold were isolated from the foliose lichen Parmotrema tsavoense. These compounds were structurally elucidated by extensive NMR analyses, comparison between experimental and theoretical 13C NMR data and X-ray crystallography. A putative biosynthetic scenario for the formation of 1-3 from parmosidone D, a meta-depsidone previously isolated from the same lichen material, was proposed. Tested for its cytotoxicity, 1 displayed a moderate activity against human myelogenous leukemia K562 cell line with an IC50 value of 66 μg mL-1. © 2018 The Royal Society of Chemistry.

Piecewise linear optimization is one of the most frequently used optimization models in practice, such as transportation, finance and supply-chain management. In this paper, we investigate a particular piecewise linear optimization that is optimizing the norm of piecewise linear functions (NPLF). Specifically, we are interested in solving a class of Brugnano–Casulli piecewise linear systems (PLS), which can be reformulated as an NPLF problem. Speaking generally, the NPLF is considered as an optimization problem with a nonsmooth, nonconvex objective function. A new and efficient optimization approach based on DC (Difference of Convex functions) programming and DCA (DC Algorithms) is developed. With a suitable DC formulation, we design a DCA scheme, named l1-DCA, for the problem of optimizing the l1-norm of NPLF. Thanks to particular properties of the problem, we prove that under some conditions, our proposed algorithm converges to an exact solution after a finite number of iterations. In addition, when a nonglobal solution is found, a numerical procedure is introduced to find a feasible point having a smaller objective value and to restart l1-DCA at this point. Several numerical experiments illustrate these interesting convergence properties. Moreover, we also present an application to the free-surface hydrodynamic problem, where the correct numerical modeling often requires to have the solution of special PLS, with the aim of showing the efficiency of the proposed method.

Beam-column joints are commonly considered critic regions for RC frames subjected to earthquake. That is why assessing the beam-column joint capacity is an important topic, especially for structures constructed before the modern seismic design codes, or for buildings in post-seismic situations. Among the in-situ structural assessment methods, the vibrational testing is currently mentioned. The authors have developed an analytical method to assess the damage evolution of a structure in function of its dynamic characteristics. The method consists of two main steps and the first one necessitates a robust model which can reproduce the static behavior of the studied structure. For this purpose, the authors try and assess the relevancy of existing numerical models to choose the most relevant for the second step. This paper presents an assessment of the CDP (Concrete Damage Plasticity) model implemented in the Abaqus software. First, an experimental study on a RC beam-column frames is presented. Unloading-reloading cycles were performed during the tests and the displacement fields were recorded by using the image correlation technique. The experimental data are used to assess the relevancy of the CDP model, but these data can be useful also for the further studies to verify and improve the accuracy of the numerical or analytical models.

The shear design of concrete slabs is still an unsolved problem. The following study presents experimental and numerical investigations on the shear behaviour of reinforced concrete slabs (without shear reinforcement) under concentrated loads. The small thick slabs of 10 cm were tested in this study. Experimental tests were conducted to quantify the shear strength and the associated failure modes. The influence of several variables was addressed such as the influence of boundary conditions, four supported side slabs instead of two supported side slabs, the influence of loading plate length. A series of eight tests on six slabs were presented. The experiments are firstly used to evaluate the pertinence of Eurocode 2 and Model Code 2010 formulations using the levels of approximation LoA I and LoA II for the shear design of reinforced concrete slabs without shear reinforcement in comparison with the French approach, and secondly validated numerical modelling using the non-linear finite element method. The proposed numerical model showed good agreement with the experimental results in terms of slab behaviour.; La conception au cisaillement de dalles en béton reste encore un problème irrésolu. L'étude suivante présente des investigations numérique et expérimentale sur le comportement au cisaillement de dalles en béton armé (sans renforcement au cisaillement) sous charge localisée. Des dalles de faible épaisseur (10cm) ont été testées dans cette étude. Les essais ont permis de quantifier la résistance au cisaillement et les modes de rupture associés. L'influence de plusieurs paramètres a été étudiée telles que les conditions-limites ou les dimensions du plateau de chargement. Une série de 8 essais sur 6 dalles est présentée. Les expériences ont été dans un premier temps, utilisées pour évaluer la pertinence des formules de l'Eurocode 2 et du ModelCode 2010 en utilisant les niveaux d'approximation LoAI et LoAII pour le dimensionnement au cisaillement de dalles en béton armé sans renforcement au cisaillement en comparaison de l'approche française. Dans un second temps, les résultats ont été validés numériquement par une méthode aux éléments finis non-linaires. Le modèle numérique proposé a montré une bonne adéquation avec les résultats expérimentaux en termes de de comportement de dalle.

International audience; Fused silica direct bonding is of particular interest for optical system manufacturing for spatial applications. However, in order to validate the European Space Agency standards, a better understanding of the assemblies mechanical behavior is required. Therefore, it is important to develop some predictive tools to determine numerically mechanical strength of complex assemblies. In this paper, a cohesive zone model is proposed to model the direct bonding interface behavior. In order to determine the mechanical strength of the interface, a propagation test, and an initiation test on a free edge the cleavage test have been performed on direct bonded fused silica samples. The FIT test (Flexible Initiation Test) is also used to identify the properties of the direct bonding joint. At the end, a comparative analyses is proposed between experimental results and finite elements models of the propagation and initiation tests.

The fuel cell is an electrochemical energy converter that directly converts the chemical energy of the fuel into electrical current and heat. The fuel cell has been able to identify itself as a source of clean energy over the past few decades. In order to achieve the durability and stability of fuel cells, many parameters should be considered and evaluated Therefore, in this study, a single-channel high-temperature polymer exchange membrane fuel cell (HT-PEMFC) has been numerically simulated in three-dimensional, isothermal and single-phase approach. The distribution of the hydrogen and oxygen concentrations, as well as water in the anode and cathode, are shown, then the effect of different parameters of the operating pressure, the gas diffusion layer porosity, the electrical conductivity of the gas diffusion layer, the ionic conductivity of the membrane and the membrane thickness are investigated and evaluated on the fuel cell performance. The results showed that the pressure drop in the cathode channel was higher than the anode channel, so that the pressure drop in the cathode channel was higher than 9 bars but, in the anode channel was equal to 2 bars. By examining the species concentration, it was observed that their concentration at the entrance was higher and at the output was reduced due to participation in the reaction and consumption. Also, with increasing the operating pressure, the electrical conductivity of the gas diffusion layer and ionic conduction of the membrane, the performance of the fuel cell is improved.

In this paper, we first conduct an exhaustive literature review on how environmental externalities in a life cycle model could be valued and, through a case study, we check the consistency of the results obtained based on different monetization models. Then we compare the two approaches for internalization of externalities in the price of products: (1) to introduce a corrective tax equal to the externalities and (2) to apply reduced value added tax rates on environmentally friendly goods based on their relatively low externalities compared to less friendly alternatives. A typical product category is selected for the case study, i.e., electrical energy derived from the two distinct primary energy sources, renewable and non-renewable. The results comparing the three monetization methods illustrate that the choice of method used can influence not only the resulting monetary value of the externalities, or marginal social costs, of a single product but also the relative ranking among alternatives in the same product category. Our results also show that internalizing externalities by means of either a corrective tax (approach 1) or a reduced value added tax rate (approach 2) eliminates the price disadvantage of green products like electricity from biomass, making them a preferable choice over cheap conventional ones like coal.