A Variable Kinematic Multifield Model for the Lamb Wave Propagation Analysis in Smart Panels

The present paper assessed the use of variable kinematic two-dimensional elements in the dynamic analysis of Lamb waves propagation in an isotropic plate with piezo-patches. The multi-field finite element model used in this work was based on the Carrera Unified Formulation which offers a versatile application enabling the model to apply the desired order theory. The used variable kinematic model allowed for the kinematic model to vary in space, thereby providing the possibility to implement a classical plate model in collaboration with a refined kinematic model in selected areas where higher order kinematics are needed. The propagation of the symmetric ((Formula presented.)) and the antisymmetric ((Formula presented.)) fundamental lamb waves in an isotropic strip was considered in both mechanical and piezo-elastic plate models. The convergence of the models was discussed for different kinematics approaches, under different mesh refinement, and under different time steps. The results were compared to the exact solution proposed in the literature in order to assess and further determine the effects of the different parameters used when dynamically modeling a Lamb wave propagating in such material. It was shown that the higher order kinematic models delivered a higher accuracy of the propagating wave evaluated using the corresponding Time Of Flight (TOF). Upon using the appropriate mesh refinement of 2000 elements and sufficient time steps of 4000 steps, the error between the TOF obtained analytically and numerically using a high order kinematics was found to be less than 1% for both types of fundamental Lamb waves (Formula presented.) and (Formula presented.). Node-dependent kinematics models were also exploited in wave propagation to decrease the computational cost and to study their effect on the accuracy of the obtained results. The obtained results show, in both the mechanical and the piezo-electric models, that a reduction in the computational cost of up to 50% can be easily attained using such models while maintaining an error inferior to 1%

A-Kinase Anchoring in Dendritic Cells Is Required for Antigen Presentation

BACKGROUND: Dendritic cells (DC) are the most potent antigen presenting cells (APC) of the immune system. Prostaglandin E(2), cyclic AMP, and protein kinase A (PKA) have all been shown to regulate DC maturation and activity. In other cells, the ability of these molecules to convey their signals has been shown to be dependent on A-kinase anchoring proteins (AKAPs). Here we present evidence for the existence and functional importance of AKAPs in human DC. METHODOLOGY/PRINCIPAL FINDINGS: Using immunofluorescence and/or western analyses we identify AKAP79, AKAP149, AKAP95, AKAP LBC and Ezrin. We also demonstrate by western analysis that expression of AKAP79, AKAP149 and RII are upregulated with DC differentiation and maturation. We establish the functional importance of PKA anchoring in multiple aspects of DC biology using the anchoring inhibitor peptides Ht31 and AKAP-IS. Incubation of protein or peptide antigen loaded DC with Ht31 or AKAP-IS results in a 30-50% decrease in antigen presentation as measured by IFN-gamma production from antigen specific CD4(+) T cells. Incubation of LPS treated DC with Ht31 results in 80% inhibition of TNF-alpha and IL-10 production. Ht31 slightly decreases the expression of CD18 and CD11a and CD11b, slightly increases the basal expression of CD83, dramatically decreases the LPS stimulated expression of CD40, CD80 and CD83, and significantly increases the expression of the chemokine receptor CCR7. CONCLUSIONS: These experiments represent the first evidence for the functional importance of PKA anchoring in multiple aspects of DC biology

Cysteinyl leukotrienes: multi-functional mediators in allergic rhinitis

Cysteinyl leukotrienes (CysLTs) are a family of inflammatory lipid mediators synthesized from arachidonic acid by a variety of cells, including mast cells, eosinophils, basophils, and macrophages. This article reviews the data for the role of CysLTs as multi-functional mediators in allergic rhinitis (AR). We review the evidence that: (1) CysLTs are released from inflammatory cells that participate in AR, (2) receptors for CysLTs are located in nasal tissue, (3) CysLTs are increased in patients with AR and are released following allergen exposure, (4) administration of CysLTs reproduces the symptoms of AR, (5) CysLTs play roles in the maturation, as well as tissue recruitment, of inflammatory cells, and (6) a complex inter-regulation between CysLTs and a variety of other inflammatory mediators exists.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75432/1/j.1365-2222.2006.02498.x.pd

Improvement of the electrical conductivity of carbon fiber reinforced polymer by incorporation of nanofillers and the resulting thermal and mechanical behavior

International audienc

Integration of piezoelectric transducers (PZT and PVDF) within polymer-matrix composites for structural health monitoring applications: new success and challenges

International audienceThis article investigates the interest of using in-situ piezoelectric (PZTand PVDF) disks to perform real-time Structural Health Monitoring(SHM) of glass fiber-reinforced polymer composites submitted to varioustensile loadings. The goal is to evaluate the working range andSHM potential of such embedded transducers for relatively simplemechanical loadings, with the long-term aim of using them to monitorcomplete 3D structures submitted to more complex loadings. SHM isperformed acquiring the electrical capacitance variation of theembedded transducers. To study the potential links between the insitucapacitance signal and the global response of the loaded hostspecimens, a multi-instrumentation composed of externalNondestructive Testing techniques was implemented on the surfacesof the specimens to search for multi-physical couplings between theseexternal measurements and the capacitance curves. Results confirmedthe non-intrusiveness of the embedded transducers, and allowedestimating their working domain. PZT capacitance signal follows wellthe mechanical loadings, but the piezoceramic transducer getsdamaged after a determined relatively low strain level due to itsbrittleness. The limits of this working domain are extended by usinga stretchable PolyVinylidene Fluoride (PVDF) polymer transducer,allowing this one to perform in-situ and real-time SHM of its hosttensile specimens until failure

Mechanical damage assessment of glass fibre-reinforced polymer composites using passive infrared thermography

This study deals with characterization of the damage and thermomechanical behavior of the Glass Fiber-Reinforced Polymer composite materials (GFRP), submitted to static tensile loadings, using a passive infrared thermography technique. During mechanical testing, thermal measurements are performed by means of an IR camera. The thermal data post-processing involves the analysis of both the thermal maps and the thermomechanical behavior of the material. The thermal maps analysis allows qualitative evaluation of the created material damage at high stress levels. While the thermomechanical analysis gave us a quantitative evaluation of the material damage, for both low and high stress levels, through definition of a new thermoelastic damage variable

Structural health monitoring for GFRP composite by the piezoresistive response in the tufted reinforcements

International audienc

Analysis of the impact and compression after impact behavior of tufted laminated composites

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Rapid estimation of the fatigue limit of Smart Polymer-Matrix Composites (PMC) using the self-heating tests

Given it is usually highly problematic and time-consuming to evaluate the real in-situ damage and fatigue limit of the polymer-matrix composite (PMC) materials, this study investigates the electrical capacitance variation of polyvinylidene difluoride (PVDF) piezopolymer transducer embedded within PMC specimens made with a polyester resin reinforced by 2/2 twill glass fabrics and submitted to the self-heating tests. During the successive cyclic loadings, the non-intrusiveness of the PVDF sensors was ensured as well as the conformity of the fatigue limit estimated using both stabilized temperature and capacitance measurements. Novel damage estimation curves were proposed based on different temperature and capacitance variables. Thereby, the originality of this study lies in the assessment of the fatigue limit and damage quantification of PMC materials using two physical magnitudes: electrical capacitance and temperature variations. These two quantities provide a fairly fast estimation of the fatigue limit with a slight percentage difference of 9%