Effects of internal pore pressure on closed-cell elastomeric foams

AbstractA micromechanics framework for porous elastomers with internal pore pressure (Idiart and Lopez-Pamies, 2012) is used together with an earlier homogenization estimate for elastomers containing vacuous pores (Lopez-Pamies and Ponte Castañeda, 2007a) to investigate the mechanical response and stability of closed-cell foams. Motivated by applications of technological interest, the focus is on isotropic foams made up of a random isotropic distribution of pores embedded in an isotropic matrix material, wherein the initial internal pore pressure is identical to the external pressure exerted by the environment (e.g. atmospheric pressure). It is found that the presence of internal pore pressure significantly stiffens and stabilizes the response of elastomeric foams, and hence that it must be taken into account when modeling this type of materials

Effective-medium theory for infinite-contrast two-dimensionally periodic linear composites with strongly anisotropic matrix behavior: Dilute limit and crossover behavior

The overall behavior of a two-dimensional lattice of voids embedded in an anisotropic elastic matrix is investigated in the limit of vanishing porosity f. An effective-medium model (of the Clausius-Mossoti type), which accounts for elastic interactions between neighboring voids, is compared to fast Fourier transform numerical solutions and, in the limits of infinite anisotropy, to exact results. A crossover between regular and singular dilute regimes is found, driven by a characteristic length which depends on f and on the anisotropy strength. The singular regime, where the leading dilute correction to the elastic moduli is an O(f1/2), is related to strain localization and to change in character—from elliptic to hyperbolic—of the governing equations

APPLICATIONS OF VORONOI AND DELAUNAY DIAGRAMS IN THE SOLUTION OF THE GEODETIC BOUNDARY VALUE PROBLEM

Voronoi and Delaunay structures are presented as discretization tools to be used innumerical surface integration aiming the computation of geodetic problemssolutions, when under the integral there is a non-analytical function (e. g., gravityanomaly and height). In the Voronoi approach, the target area is partitioned intopolygons which contain the observed point and no interpolation is necessary, onlythe original data is used. In the Delaunay approach, the observed points are verticesof triangular cells and the value for a cell is interpolated for its barycenter. If theamount and distribution of the observed points are adequate, gridding operation isnot required and the numerical surface integration is carried out by point-wise. Evenwhen the amount and distribution of the observed points are not enough, thestructures of Voronoi and Delaunay can combine grid with observed points in orderto preserve the integrity of the original information. Both schemes are applied to thecomputation of the Stokes’ integral, the terrain correction, the indirect effect and thegradient of the gravity anomaly, in the State of Rio de Janeiro, Brazil area

Borderline CD30+ Cutaneous Lymphoproliferative Disorder: Report of a Case with Expression of Cytotoxic Markers and Response to Clarithromycin

CD30+ cutaneous lymphoproliferative disorders (CLPDs) are usually characterized by a benign clinical course. The prognostic value of cytotoxic markers in these lymphomas has not been evaluated in large series. We describe a case of borderline CD30+ CLPD with cytotoxic phenotype, presenting in a 22-year-old male patient as an ulcer on the forearm. He reported having had similar ulcers on the buttock and thigh that spontaneously regressed over the course of 1 year. The lesion resolved with a single course of clarithromycin; a subsequent lesion, too, responded to clarithromycin, and no recurrences or systemic involvement have been documented in the 9-month follow-up. A conservative approach in the management of CD30+ CLPD is recommended. We believe that the anti-inflammatory and apoptotic effects of clarithromycin on T cells may have hastened the remission process

Sequence analysis of a genomic clone encoding a Zc2 protein from Zea mays W64A

A genomic clone (p268c) coding for the 28 kD storage protein Zc2 from maize endosperm has been isolated and sequenced

Unimodularity and invariant volume forms for Hamiltonian dynamics on Poisson-Lie groups

In this paper, we discuss several relations between the existence of invariant volume forms for Hamiltonian systems on Poisson-Lie groups and the unimodularity of the Poisson-Lie structure. In particular, we prove that Hamiltonian vector fields on a Lie group endowed with a unimodular Poisson-Lie structure preserve a multiple of any left-invariant volume on the group. Conversely, we also prove that if there exists a Hamiltonian function such that the identity element of the Lie group is a nondegenerate singularity and the associated Hamiltonian vector field preserves a volume form, then the Poisson-Lie structure is necessarily unimodular. Furthermore, we illustrate our theory with different interesting examples, both on semisimple and unimodular Poisson-Lie groups.Comment: 17 page

The effect of music-induced emotion on visual-spatial learning in people with Parkinson's disease: A pilot study

Introduction: Emotional states have been shown to influence cognitive processes including visual-spatial learning. Parkinson's Disease (PD), besides manifesting with the cardinal motor symptoms, presents cognitive and affective disturbances. Here we aimed at investigating whether manipulation of the emotional state by means of music was able to influence the performance of a visual-spatial learning task in a group of PD participants. Methods: Ten PD patients and 11 healthy elderly (ELD) were asked to perform a visual-spatial learning task while listening two musical pieces evoking a neutral emotion or fear. Targets were presented on a screen in a preset order over four blocks and subjects were asked to learn the sequence order by attending to the display. At the end of each block, participants were asked to verbally recall the sequence and a score was assigned (Verbal Score, VS). Results: Analysis of variance-type statistic test on the VS disclosed a significant effect of Music and sequence Blocks (p = 0.01 and p < 0.001, respectively) and a significant interaction between Group and sequence Blocks. Sequence learning occurred across the training period in both groups, but PD patients were slower than ELD and at the end of the training period learning performance was worse in PD with respect to ELD. In PD patients, like in ELD, fear-inducing music has a detrimental effect on visual-spatial learning performances, which are slower and decreased. Conclusion: These findings confirm an impairment in visual-spatial learning in PD and indicates that the emotional state influences this learning ability similarly to healthy controls

Selección perceptual en rivalidad binocular: experimentos con series rápidas de estímulos visuales

Ponència de la VI Reunión Científica sobre Atención (RECA 6), celebrada a Barcelona, 200

Reentrant behaviour in Landau Fermi liquids with spin-split Pomeranchuk instabilities

We study the effects of spin-antisymmetric interactions on the stability of a Landau-Fermi liquid on the square lattice, using the generalized Pomeranchuk method for two-dimensional lattice systems. In particular, we analyze interactions that could induce instabilities of the so called spin-split type, that is when spin-up and spin-down Fermi surfaces are displaced with respect to each other. The phase space is studied as a function of the strength of the interaction $V$, the electron chemical potential $\mu$ and an external magnetic field $h$. We find that such interactions produce in general an enhancement of the instability region of the Landau-Fermi liquid. More interestingly, in certain regions of the $V$-$\mu$ phase space, we find a reentrant behaviour as a function of the magnetic field $h$, similar to that found in recent experiments, e.g. in URu$_2$Si$_2$ and Sr$_3$Ru$_2$O$_7$.Comment: 5 pages, 3 figure