Nonlinear isotropic constitutive laws: choice of the three invariants, convex potentials and constitutive inequalities

The aim of this paper is a new formulation of nonlinear isotropic constitutive laws. Our main hypothesis claims that the eigenvalues of stress and strain tensors are classified in the same order (the eigenvector associated to the highest eigenvalue of the stress tensor is also associated to the highest eigenvalue of the strain tensor, etc.). Further, we assume the existence of a differentiable convex isotropic potential. By introducing three new invariants for each tensor (called X, Y, Z for the stress tensor S and x, y, z for the strain tensor E) a constitutive law is revealed to be a simple duality between the chosen invariants: (x, y, z) and (X, Y, Z) look like Cartesian coordinates of E and S. We look at several potentials chosen as polynomials of these invariants. Finally, first and third order isotropic elasticity laws are reviewed and convexity of the potentials is discussed.     

Acousto-optically driven lensless single-shot ultrafast optical imaging

Driven by many applications in a wide span of scientific fields,a myriad of advanced ultrafast imaging techniques have emerged in the last decade,featuring reco...     

The role of activity restriction in poststroke depressive symptoms.

Objective: Little is known about the determinants of poststroke depression. The Activity Restriction Model of Depressed Affect (ARMDA) may be helpful in understanding poststroke depression but has never been tested in that context. The goal of this study was to examine the relation between activity restriction and depressive symptoms in stroke survivors during the period following discharge from the hospital. Method: Participants (N = 197) were assessed on three occasions: (1) time 1 (T1), 3 weeks following discharge; (2) time 2 (T2), 3 months after discharge; and (3) time 3 (T3), 6 months after discharge. Results: Although both stroke severity and activity restriction were significantly related to depressive symptoms, the relation between stroke severity and depression was no longer significant after controlling for activity restriction. Moreover, restrictions in daily activities and social roles were both related to depressive symptoms, but these relations were found to vary during the course of the period following discharge. Conclusions: These findings support the ARMDA and have practical implications for the prevention of poststroke depression. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Analysis of the medical and biological pain research literature in the European Union: A 2006 snapshot

This study analyzed 2443 papers published in 2006 by European Union authors on pain-related research. Five EU countries (the UK, Germany, Italy, the Netherlands and France) each published > 200 papers while three countries (Cyprus, Malta and Estonia) published none; socio-economic indicators were related to each country’s productivity. The 2443 papers were published in 592 journals and Cephalalgia, Pain and European Journal of Pain were the most prolific. Publications were also analyzed for intra- versus inter-EU/non-EU collaborations and subdisciplines profiles in Clinical Medicine and the Life Sciences for the World, USA, EU and the top-four EU countries were compared.     

Effect of oxide additives and particle size on stabilization of treated commercial zirconia

Commercial zirconia was milled and sedimented to separate finer and coarser particles. Then additives such as CaO and Y₂O₃ were added in proportions of 7 and 13 mol.% each. Wet mixing of these powders was done in the ball mill. These mixtures were then compacted through uniaxial compaction using 150 MPa of pressure to make pellets of 8 mm diameter and 3 mm height approximately. The compacts were sintered at 1700 °C under argon atmosphere during 1 h. Densification calculations revealed densities of more than 80% in all samples. Scanning electron microscopy (SEM) showed that closed porosity was present. X-ray diffraction (XRD) results confirmed the presence of cubic phase with quantities higher in samples of finer powder and 13 mol.% additive.     

Diagnosis Method Using ΔIDDQ Probabilistic Signatures: Theory and Results

This paper presents a diagnostic method based on differential I_DDQprobabilistic signatures, inspired by telecommunications systems. The method and its unique features are described. Then, results from an IC monitor containing controllable faults show the capability of the method to diagnose actual activated faults, despite a strong experimental current standard variation. These results validate previous simulation procedures, which are applied to quantify effects not covered by the monitor experiment, that is, the effect of the load of a bridged node and the effect of the bridge resistance value. These experimental and simulation results reveal the robustness of the proposed diagnosis method, that has identified and located every single fault considered so far.     

Maximal feedback linearization and its internal dynamics with applications to mechanical systems on

For systems that are not feedback linearizable, a natural question is: how to find the largest feedback linearizable subsystem and, if the partial linearization is not unique, what are the control‐theoretic properties of various partial linearizations. In this paper, we will consider the problem of how to choose a partially linearizing output that renders the zero dynamics asymptotically stable and when such an output exists. We will state general results solving completely the problem for systems whose linearizability defect is one by identifying and describing two classes of systems. For the first class, all maximal partial linearizations lead to the same zero dynamics. For the second class, any asymptotic behavior of the zero dynamics can be achieved by a suitable choice of a partially linearizing output. In the second part, we apply our results to mechanical systems with two‐degrees‐of‐freedom and provide a detailed study of their partial linearizations. We illustrate the obtained results by examples of Acrobot (which belongs to the second class) and Pendubot (which belongs to the first class).     

Al matrix composites reinforced by in situ synthesized graphene–Cu hybrid layers: interface control by spark plasma sintering conditions

Journal of Materials Science - Tremendous impacts are usually made by the synthesis method and consolidation technique on microstructure and interface of graphene/Al composites. In the present...     

Adaptation of the Romanomermis culicivorax CCA-Adding Enzyme to Miniaturized Armless tRNA Substrates

The mitochondrial genome of the nematode Romanomermis culicivorax encodes for miniaturized hairpin-like tRNA molecules that lack D- as well as T-arms, strongly deviating from the consensus cloverleaf. The single tRNA nucleotidyltransferase of this organism is fully active on armless tRNAs, while the human counterpart is not able to add a complete CCA-end. Transplanting single regions of the Romanomermis enzyme into the human counterpart, we identified a beta-turn element of the catalytic core that—when inserted into the human enzyme—confers full CCA-adding activity on armless tRNAs. This region, originally identified to position the 3′-end of the tRNA primer in the catalytic core, dramatically increases the enzyme’s substrate affinity. While conventional tRNA substrates bind to the enzyme by interactions with the T-arm, this is not possible in the case of armless tRNAs, and the strong contribution of the beta-turn compensates for an otherwise too weak interaction required for the addition of a complete CCA-terminus. This compensation demonstrates the remarkable evolutionary plasticity of the catalytic core elements of this enzyme to adapt to unconventional tRNA substrates.