A new triangular and tetrahedral basis for high-order (hp) finite element methods

In this paper we describe the foundations of a new hierarchical modal basis suitable for high-order (hp) finite element discretizations on unstructured meshes. It is based on a generalized tensor product of mixed-weight Jacobi polynomials. The generalized tensor product property leads to a low operation count with the use of sum factorization techniques. Variable p-order expansions in each element are readily implemented which is a crucial property for efficient adaptive discretizations. Numerical examples demonstrate the exponential convergence for smooth solutions and the ability of this formulation to handle easily very complex two- and three-dmensional computational domains employing standard meshes.     

Developing hope in the social context: Alternative perspectives of motive, meaning, and identity.

C. R. Snyder, J. Cheavens, and S. C. Sympson (1997) presented a developmental model of hope embedded within a social-cognitive framework. This is a feature common to most contemporary theories of reality negotiation processes. However, in this comment on the Snyder et al piece, the authors believe that there are alternative accounts of the goal-directed behavior associated with hope that warrant consideration. They briefly describe these competing accounts available in Kohutian self psychology and in multicultural models of behavior. They note points of convergence and divergence, along with implications for clinical practice and theory-driven research. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Toward shielding improvements in MRI gradients and other systems.

A new method is described for reducing the shielding-error function in the 'supershielding' approach to designing MRI systems. The method is thus shown to lead to significantly better shielding and better control of eddy current effects associated with gradient coils. To illustrate this technique, a set of results for a z-gradient coil is presented. A generalization to non-standard geometries can be made in a straightforward manner with the new method. The usefulness of the relationship of all fringe-field quantities to the shielding-error function is emphasized. The formal limit of perfect shielding in a 'least-squares' sense is shown for a simple strip-shield model along with a numerical eigenvalue study for comparison with the theoretical limit.     

Steroid hormones, memory and mood in a healthy elderly population

Men (n = 31), women estrogen-users (n = 14), and women estrogen non-users (n = 41), whose average age was 72.1 +/- 5.6 years, were tested with a battery of psychological tests measuring verbal memory, visual memory, concentration and attention, language fluency and semantic memory, and mood. Plasma levels of testosterone (T), estradiol (E2), cortisol (CRT) and dehydroepiandrosterone-sulfate (DHEAS) were assessed by radioimmunoassay. The ratio of DHEAS to CRT was calculated to determine it's relationship to memory functioning. The men had higher T and DHEAS levels than both groups of women. Women estrogen-users had higher E2 levels than both men and estrogen non-users and the men had higher E2 levels and a higher DHEAS/CRT ratio than the estrogen non-users. There were no group differences in CRT levels. Men and estrogen-users had higher total (p < .01) and forward (p < .001) digit span scores compared with non-users. Women estrogen-users also had higher backward digit span scores than non-users (p < .05), while both groups of women performed better than men on category retrieval (p < .01). The implications of these findings with respect to hormonal influences on memory in elderly men and women are discussed.     

rp-adaptation for compressible flows

We present a novel rp-adaptation strategy for high-fidelity simulations of compressible inviscid flows with shocks. The mesh resolution in regions of flow discontinuities is increased by using a variational optimizer to r-adapt the mesh and cluster degrees of freedom there. In regions of smooth flow, we locally increase or decrease the local resolution through increasing or decreasing the polynomial order of the elements, respectively. This dual approach allows us to take advantage of the strengths of both methods for best computational performance, thereby reducing the overall cost of the simulation. The adaptation workflow uses a sensor for both discontinuities and smooth regions that is cheap to calculate, but the framework is general and could be used in conjunction with other feature-based sensors or error estimators. We demonstrate this proof-of-concept using two geometries in transonic and supersonic flow regimes. The method has been implemented in the open-source spectral/hp element framework Nektar++, and adaptivity is performed by its dedicated high-order mesh generation tool NekMesh. The results show that the proposed rp-adaptation methodology is a reasonably cost-effective way of improving simulation accuracy.     

‘Little wake turbulence,huh?’ Applying a contemporary model of learning and memory to the American Airlines Flight AA587 accident

Loss of control has become a leading cause of aviation accidents and human error is often recorded as the cause in favour of other factors. This has the effect of downgrading the significance of corrective actions to address deeper systemic issues, and serves the bad-apple theory of human error. This paper uses a model of learning and memory to expand on the analysis of negative training from the AA587 accident, which documented the actions of the First Officer as the probable cause and training as contributory. Evidence from the investigation and our contemporary understanding of learning and memory is used to explain how the experiences of the First Officer fit the scenario in which the accident occurred, such that it is plausible to extend probable cause beyond his actions. The paper develops a model of causal inference that enables analysts to continue probing causality as part of a systems approach.     

Effect of reverse flow on the pattern of wall shear stress near arterial branches

Atherosclerotic lesions have a patchy distribution within arteries that suggests a controlling influence of haemodynamic stresses on their development. The distribution near aortic branches varies with age and species, perhaps reflecting differences in these stresses. Our previous work, which assumed steady flow, revealed a dependence of wall shear stress (WSS) patterns on Reynolds number and side-branch flow rate. Here, we examine effects of pulsatile flow. Flow and WSS patterns were computed by applying high-order unstructured spectral/hp element methods to the Newtonian incompressible Navier–Stokes equations in a geometrically simplified model of an aorto-intercostal junction. The effect of pulsatile but non-reversing side-branch flow was small; the aortic WSS pattern resembled that obtained under steady flow conditions, with high WSS upstream and downstream of the branch. When flow in the side branch or in the aortic near-wall region reversed during part of the cycle, significantly different instantaneous patterns were generated, with low WSS appearing upstream and downstream. Time-averaged WSS was similar to the steady flow case, reflecting the short duration of these events, but patterns of the oscillatory shear index for reversing aortic near-wall flow were profoundly altered. Effects of reverse flow may help explain the different distributions of lesions.     

Hormones, the brain, and me.

My research program in psychoneuroendocrinology, a subdiscipline of psychology, has focused on the investigation of three areas of women's health. First, the authors have studied the role of androgen in female sexuality; second, the authors have investigated the effects of estrogen on mood in women, and more recently, the authors have demonstrated the conditions under which estrogen treatment would be neuroprotective with regard to cognitive functioning in aging women. The results of our own and of other researchers' studies in all three areas of psychoneuroendocrinology are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Importance of cerebral blood flow to the recognition of and physiological responses to hypoglycemia

1. Glibenclamide, a blocker of ATP-sensitive potassium channels, has been shown to antagonize relaxin as a uterine relaxant in the rat in vivo but not in vitro. The aim, therefore, was to investigate whether the discrepancy between the two studies was a consequence of differences in (1) muscle layers, (2) hormonal conditions or (3) spasmogens utilized. Relaxin was compared with salbutamol and levcromakalim. 2. Relaxin was of similar potency as a uterine relaxant against oxytocin (0.2 mM)-induced spasm with tension measured in the circular or longitudinal muscle layers. Glibenclamide (10 microM) did not antagonize relaxin or salbutamol in these preparations but greatly antagonized levcromakalim (91-fold). Relaxin was a relaxant of tension activated by transmural electrical stimulation in uteri from rats that had been ovariectomized, although the maximal effect was only 30 +/- 15%, and in uteri from rats that had been treated with 17 beta-estradiol benzoate. Glibenclamide was not an antagonist of relaxin in the latter preparation but did antagonize levcromakalim (118-fold). Relaxin also inhibited spontaneous phasic tension development in uteri from ovariectomized rats but again was not antagonized by glibenclamide. 3. Because relaxin was not antagonized by glibenclamide under any of these various conditions, it would appear that the in vivo-in vitro discrepancy in the antagonism of relaxin by glibenclamide is not attributable to the effects of different muscle layers, hormonal conditions or spasmogens. It may be that the mechanism of action of relaxin or glibenclamide or both differs between in vivo and in vitro preparations.