Quantitative imaging of nonlinear shear modulus by combining static elastography and shear wave elastography

The study of new tissue mechanical properties such as shear nonlinearity could lead to better tissue characterization and clinical diagnosis. This work proposes a method combining static elastography and shear wave elastography to derive the nonlinear shear modulus by applying the acoustoelasticity theory in quasi-incompressible soft solids. Results demonstrate that by applying a moderate static stress at the surface of the investigated medium, and by following the quantitative evolution of its shear modulus, it is possible to accurately and quantitatively recover the local Landau (A) coefficient characterizing the shear nonlinearity of soft tissues.     

Succinylation of Non-ionic Surfactants: Physicochemical Characterization,Functional Properties,Biodegradability and Mathematical Modeling of the Polarity Tuning

Anionic surfactants comprising succinic acid end groups were synthesized by succinylation of non-ionic surfactants using succinic anhydride as a potentially bio-sourced building block. A solvent- and catalyst-free synthesis was designed for succinic anhydride mono esterification with octyl-, decyl and dodecylpolyxylosides, di- and tetraethylene glycol dodecylethers and glycerol monolaurate. The physicochemical and functional properties of anionic surfactants thus obtained were studied and compared with their non-succinylated counterparts. A correlation between these properties and the polarity changes induced by the addition of the hydrophilic succinic acid moiety was established. The biodegradability of the succinylated surfactants has also been investigated. Finally, through a desirability function approach, mathematic predictions were correlated to the properties in order to find an optimum and to discriminate surfactants with respect to targeted physicochemical properties and resulting applications.     

Characterization of Olive-Leaf Phenolics by ESI-MS and Evaluation of their Antioxidant Capacities by the CAT Assay

Olive leaves are a very abundant vegetable material containing various phenolic compounds, such as secoiridoids and flavonoids, that are expected to exert strong antioxidant capacity. However, little is known about the variation of olive-leaf phenolic composition during maturation and its influence on antioxidant capacity. To answer this question, young and mature Olea Europaea L. leaves were submitted to successive extraction with dichloromethane, ethyl acetate, and methanol, then characterized by ESI-MS. It appeared that mature olive-leaf extracts contained higher levels of verbascoside isomers and glucosylated forms of luteolin, while young ones presented higher contents of oleuropein, ligstroside, and flavonoid aglycones. Moreover, antioxidant capacity evaluation using our newly developed conjugated autoxidizable triene assay showed that, in a lipid-based emulsified system, this phenolic composition variation leads to a change in the ability of extracts to counteract lipid oxidation. Mature olive-leaf extracts exhibit higher antioxidant capacity than young olive-leaf extracts. This result enables us to hypothesize that two main bioconversion scenarios may occur during maturation of olive leaves, which could explain changes observed in antioxidant capacity: (1) a bioconversion of oleuropein and ligstroside into verbascoside isomers and oleuroside, and (2) a bioconversion of flavonoid aglycones into glucosylated forms of luteolin. Finally, this study leads to a better understanding of the relationship between phenolic profile and antioxidant capacity of olive leaves.     

Modeling of ultrasonic wave propagation in integrated piezoelectric structures under residual stress

The objective of this study is to understand the role of residual stress in piezoelectric layers in order to predict the performance of integrated structures. This is of particular importance in thick or thin film technology. Considering a bulk piezoelectric material, the Christoffel equation for a piezoelectric material is modified to take into account a uniform residual stress on a given cross section. A numerical study of its influence is carried out on the slowness curves and coupling coefficients of a lithium niobate material. In a second part, modified Christoffel tensor is used to calculate the dispersion curves of Lamb waves in a piezoelectric plate. The Lamb modes are found to be sensitive to the residual stress. In particular, it is shown how the behavior of the first Lamb modes is modified with residual stress. In a third part, these results are extended to a piezoelectric film laid down on a substrate in order to model the importance of these phenomena on the behavior of an integrated structure. The numerical study of guided waves in a lithium niobate plate is performed first, then the case of a lithium niobate film laid down on a silicon substrate is considered.     

Optimized dynamic compilation of dataflow representations for multimedia applications

This paper proposes two optimization methods based on dataflow representations and dynamic compilation that enhance flexibility and performance of multimedia applications. These optimization methods are intended to be used in an adaptive decoding context, or, in other terms, where decoders have the ability to adapt their decoding processes according to a bitstream. This adaptation is made possible by coupling the decoding information to process a stream inside a coded stream. In this paper, we use dataflow representations from the upcoming MPEG Reconfigurable Media Coding (RMC) standard to supply the decoding information to adaptive decoders. The benefits claimed by MPEG RMC are a reuse of coding tools between different specifications of decoder and an execution scalability on different processing units with a single specification, which can target either hardware and/or software platforms. These benefits are not yet achievable in practice as these specifications are not used at the receiver side in MPEG RMC. We valid these benefits and propose two optimizations for the generation and the execution of dataflow models: the first optimization takes benefits of the reuse of coding tools to reduce the time to obtain—configure—enforceable decoders. The second provides an efficient, dynamic, and scalable execution according to the features of the execution platform. We show the practical impact of these two optimizations on two decoder representations compliant with the MPEG-4 part 2 Simple Profile standard and the MPEG-4 Advanced Video Coding standard. The results shows that configuration time can be reduced by 3 and the performance of decoders can be increased by 50 %.     

MPEG Reconfigurable Video Coding: From specification to a reconfigurable implementation

This paper demonstrates that it is possible to produce automatic, reconfigurable, and portable implementations of multimedia decoders onto platforms with the help of the MPEG Reconfigurable Video Coding (RVC) standard. MPEG RVC is a new formalism standardized by the MPEG consortium used to specify multimedia decoders. It produces visual representations of decoder reference software, with the help of graphs that connect several coding tools from MPEG standards. The approach developed in this paper draws on Dataflow Process Networks to produce a Minimal and Canonical Representation (MCR) of MPEG RVC specifications. The MCR makes it possible to form automatic and reconfigurable implementations of decoders which can match any actual platforms. The contribution is demonstrated on one case study where a generic decoder needs to process a multimedia content with the help of the RVC specification of the decoder required to process it. The overall approach is tested on two decoders from MPEG, namely MPEG-4 part 2 Simple Profile and MPEG-4 part 10 Constrained Baseline Profile. The results validate the following benefits on the MCR of decoders: compact representation, low overhead induced by its compilation, reconfiguration and multi-core abilities.     

Water intrusion in mesoporous silicalite-1: An increase of the stored energy

In silicalite-1 (pure silica MFI-type zeolite), the water adsorption is extremely weak when the pressure is lower than the water saturation vapor pressure. The water condensation (intrusion) is obtained by applying a high hydraulic pressure, approximately of 100 MPa. Extrusion of water occurring at the similar pressure, the “water–silicalite-1” system constitutes thus a real molecular spring, which can store and restore mechanical energy. In order to increase the stored energy in this system, the porous volume of this zeolite was increased by the creation of additional micro-, meso- and macropores using carbon black or surfactant [3-(trimethoxysilyl)propyl]hexadecyldimethylammonium chloride, as porogen and templating agents, respectively. The presence of meso- and macropores modifies the water condensation behavior in silicalite-1. Indeed, the water intrusion takes place in two stages. The first one, from 3 to 7 MPa, corresponds to the filling of meso- and macropores but the amount of stored energy is very low. The second one, at 100 MPa, corresponds to the filling of micropores. The increase of the microporous volume leads to an increase of the intruded water volume at high hydraulic pressure. Consequently, the stored energy is greater than for a conventional silicalite-1 zeolite.     

Chemical Composition and Ability of Essential Oils from Six Aromatic Plants to Counteract Lipid Oxidation in Emulsions

Essential oils with antioxidant properties are of increasing interest in West Africa where there are many antioxidant rich plants. The objective of this study was to determine the essential oil extracted from six native plants (Lippia multiflora, Lippia rugosa, Monodora tenuifolia, Ocimum gratissimum, Pimenta racemosa, Cymbopogon citratus) extracted by hydrodistillation from local plants in Benin. These samples were also evaluated for their antioxidant capacity using the conjugated autoxidizable triene (CAT) assay performed in stripped tung oil-in-water emulsion. The essential oil of P. racemosa, containing high amounts of chavicol (10.3 %) and eugenol (54.5 %), showed the strongest antioxidant activity, followed by that from O. gratissimum containing large amounts of thymol (50.2 %). The essential oil extracted from M. tenuifolia exhibited a moderate antioxidant activity. This essential oil is primarily composed of sesquiterpene alcohols such as α-cadinol (20.5 %), its isomer, α-muurolol (14.7 %), and germacrene D-4-ol (16.8 %). Essential oils from L. multiflora, L. rugosa and C. citratus oils showed poor ability to protect tung oil from oxidation. Finally, essential oils containing phenolic compounds and, in a lesser extent, sesquiterpene alcohols, exhibited the highest CAT values indicating that these compounds are the key determinants of the antioxidant activity of these essential oils in oil-in-water emulsions.     

Relations between single-domain and multidomain piezoelastic properties in single crystals

This paper presents a new method to compute the piezoelastic properties of multidomain single crystals from the single-domain constants. Based on a quasi static assumption, a PMN-chiPT multidomain is defined as a periodic medium with a lattice composed of layers of two domains in a twin structure. Such a structure is assumed to have charged domain walls that imply specific lattice media and boundary conditions. A numerical computation has been performed for a PMN-33PT single crystal in the rhombohedral phase. The effective elastic, piezoelectric, and dielectric constants of the macroscopic structure have been calculated, as well as the wave velocities in different configurations of domain patterns.     

Evaluation methodology and theoretical model for antiviral behavioural detection strategies

Behavioural analysis for detection of malware has recently emerged as a new promising set of antiviral techniques: function-based detection is now considered along with sequence-based detection. Most of the antivirus publishers now claim to use behavioral analysis as a marketing argument. But the real impact of these “new” techniques seems to be mitigated since no real progress in the general antiviral fight has been noticed nowadays. This paper presents an evaluation methodology of the real capabilities of antivirus software with respect to the behavioral analysis. It is shown that contrary to the claims of some publishers, behavioural analysis is still very marginally used and implemented. These techniques are quite always either validated by or dependant on classical form-based detection methods (detection pattern as an example). In this context, we propose a generalised, theoretical detection model which considers at the same time both form-based and function-based detection and give some essential properties this model should exibhit to achieve a real behavioural-based detection. This paper is the extended version of the paper presented at WTCV’06 (Workshop in Theoretical Computer Virology) in Nancy, France, May 2006.