Local strain measurements of yarns inside of 3D warp interlock fabric during forming process

The final geometry of 3D warp interlock fabric needs to be check during the 3D forming step to ensure the right locations of warp and weft yarns inside the final structure. Thus, a new monitoring approach has been proposed based on sensor yarns located in the fabric thickness. To ensure the accuracy of measurements, the observation of the surface deformation of the 3D warp interlock fabric has been joined to the sensor yarns measurements. At the end, it has been revealed a good correlation between strain measurement done globally by camera and locally performed by sensor yarns. Additionally, sensor yarns located in the two directions of the 3D warp interlock fabric have revealed a different forming behaviour depending on the architecture and the different slope values of the punch.     

Boundary effect on weight function in nonlocal damage model

Some insights on boundary effects in nonlocal damage modelling are addressed. Interaction stresses that are at the origin of nonlocality are expected to vanish at the boundary of a solid, in the normal direction to this boundary. Existing models do not account for such an effect. We introduce tentative modifications of the classical nonlocal damage model aimed at accounting for this boundary layer effect in a continuum modelling setting. Computations show that some nonnegligible differences may be observed between the classical and modified formulations. In a one dimensional spalling test, only the modified formulation provides a spall of finite nonzero thickness, whereas spalls smaller than the internal length cannot be obtained according to the original formulation. For the same set of model parameters, including the internal length, the fracture energy derived from the size effect test method is also very different according to both approaches. Parameters in the size effect laws for notched and unnotched specimens, obtained from computation of geometrically similar bending beams, are more consistent with the modified nonlocal model compared to the original nonlocal formulation.     

Generalized model of resonant polymer-coated microcantilevers in viscous liquid media

Expressions describing the resonant frequency and quality factor of a dynamically driven, polymer-coated microcantilever in a viscous liquid medium have been obtained. These generalized formulas are used to describe the effects the operational medium and the viscoelastic coating have on the device sensitivity when used in liquid-phase chemical sensing applications. Shifts in the resonant frequency are normally assumed proportional to the mass of sorbed analyte in the sensing layer. However, the expression for the frequency shift derived in this work indicates that the frequency shift is also dependent on changes in the sensing layer's loss and storage moduli, changes in the moment of inertia, and changes in the medium of operation's viscosity and density. Not accounting for these factors will lead to incorrect analyte concentration predictions. The derived expressions are shown to reduce to well-known formulas found in the literature for the case of an uncoated cantilever in a viscous liquid medium and the case of a coated cantilever in air or in a vacuum. The theoretical results presented are then compared to available chemical sensor data in aqueous and viscous solutions.     

Synthetic rat V1a vasopressin receptor fragments interfere with vasopressin binding via specific interaction with the receptor

To study the vasopressin receptor domains involved in the hormonal binding, we synthesized natural and modified fragments of V1a vasopressin receptor and tested their abilities to affect hormone-receptor interactions. Natural fragments mimicking the external loops one, two, and three were able to inhibit specific vasopressin binding to V1a receptor. In contrast, the natural N-terminal part of the V1a vasopressin receptor was found inactive. One fragment, derived from the external second loop and containing an additional C-terminal cysteine amide, was able to fully inhibit the specific binding of both labeled vasopressin agonist and antagonist to rat liver V1a vasopressin receptor and the vasopressin-sensitive phospholipase C of WRK1 cells. The peptide-mediated inhibition involved specific interactions between the V1a receptor and synthetic V1a vasopressin receptor fragment since 1) it was dependent upon the vasopressin receptor subtype tested (Ki(app) for the peptide: 3.7, 14.6, and 64.5 microM for displacing [3H]vasopressin from rat V1a, V1b, and V2 receptors, respectively; 2) it was specific and did not affect sarcosin 1-angiotensin II binding to rat liver membranes; 3) it was not mimicked by vasopressin receptor unrelated peptides exhibiting putative detergent properties; and 4) no direct interaction between [3H]vasopressin and synthetic peptide linked to an affinity chromatography column could be observed. Such an inhibition affected both the maximal binding capacity of the V1a vasopressin receptor and its affinity for the labeled hormone, depending upon the dose of synthetic peptide used and was partially irreversible. Structure-activity studies using a serie of synthetic fragments revealed the importance of their size and cysteinyl composition. These data indicate that some peptides mimicking extracellular loops of the V1a vasopressin receptor may interact with the vasopressin receptor itself and modify its coupling with phospholipase C.     

Effects of oral exposure to mining waste on in vivo dopamine release from rat striatum

Several single components of mining waste (arsenic, manganese, lead, cadmium) to which humans are exposed at the mining area of Villa de la Paz, Mexico, are known to provoke alterations of striatal dopaminergic parameters. In this study we used an animal model to examine neurochemical changes resulting from exposure to a metal mixture. We used microdialysis to compare in vivo dopamine release from adult rats subchronically exposed to a mining waste by oral route with those from a control group and from a sodium arsenite group (25 mg/kg/day). We found that arsenic and manganese do accumulate in rat brain after 2 weeks of oral exposure. The mining waste group showed significantly decreased basal levels of dihydroxyphenylacetic acid (DOPAC; 66.7 +/- 7.53 pg/ microl) when compared to a control group (113.7 +/- 14.3 pg/ microl). Although basal dopamine release rates were comparable among groups, when the system was challenged with a long-standing depolarization through high-potassium perfusion, animals exposed to mining waste were not able to sustain an increased dopamine release in response to depolarization (mining waste group 5.5 +/- 0.5 pg/ microl versus control group 21.7 +/- 5.8 pg/ microl). Also, DOPAC and homovanillic acid levels were significantly lower in exposed animals than in controls during stimulation with high potassium. The arsenite group showed a similar tendency to that from the mining waste group. In vivo microdialysis provides relevant data about the effects of a chemical mixture. Our results indicate that this mining waste may represent a health risk for the exposed population.     

Numerical method for impulse control of piecewise deterministic Markov processes

This paper presents a numerical method to calculate the value function for a general discounted impulse control problem for piecewise deterministic Markov processes. Our approach is based on a quantization technique for the underlying Markov chain defined by the post jump location and inter-arrival time. Convergence results are obtained and more importantly we are able to give a convergence rate of the algorithm. The paper is illustrated by a numerical example.     

Study of viscoelastic effect on the frequency shift of microcantilever chemical sensors

Microcantilevers coated with a chemically sensitive layer are increasingly being used in chemical detection systems. The sensitive coating, often a polymer, absorbs specific molecules, which can be detected by monitoring the shift in the mechanical resonant frequency. Usually, the frequency shift resulting from molecular absorption is interpreted as a mass loading effect. However, mass loading is not the only effect that has an impact on the frequency shift; the viscoelastic properties of the sensitive coating also are affected by the sorption process. Sorption-induced modulus changes are typically difficult to characterize. However, it is known that the sorption of analyte molecules in a polymer coating results in the plasticization of the coating. In most cases, the polymer becomes more rubbery with increasing concentration of analyte molecules, i.e., the coating becomes softer with increasing loss modulus, and the storage modulus decreases. Using a new analytical model developed for the resonant frequency expression of a hybrid microcantilever (elastic base and viscoelastic layer), the effects of the modification of the storage and loss moduli of the sensitive layer on the resonant frequency are examined. The main conclusion of this analytical study is that, even if the sensitive coating moduli are small compared to the base cantilever's Young's modulus, the effect of the change in the viscoelastic coating properties could contribute significantly to the overall frequency shift (8-23% in the simulations depending on the coating thickness, with even higher contributions for other sets of problem parameters).     

Synthesis of amidrazones using an engineered papain nitrile hydratase

Diadenosine polyphosphates present at the cytosol can be transported to secretory granules allowing their exocytotic release. Extracellularly, they can act through specific metabotropic or ionotropic receptors, or as analogues of P2X and P2Y nucleotide receptors. The specific ionotropic receptor P4 is present in synaptic terminals, and modulated by protein kinases (PK) A and C and protein phosphatases. Activation of PKA or PKC, directly or through membrane receptors, results in a decrease of affinity or in reduction of the Ca2+ transient respectively. Adenosine and ATP, both products of the extracellular destruction of diadenosine polyphosphates, acting through A1 or P2Y receptors respectively, are important physiological modulators at the P4 receptor.