Finite Element Methods for a System of Dispersive Equations

The present study is concerned with the numerical approximation of periodic solutions of systems of Korteweg–de Vries type, coupled through their nonlinear terms. We construct, analyze and numerically validate two types of schemes that differ in their treatment of the third derivatives appearing in the system. One approach preserves a certain important invariant of the system, up to round-off error, while the other, somewhat more standard method introduces a measure of dissipation. For both methods, we prove convergence of a semi-discrete approximation and highlight differences in the basic assumptions required for each. Numerical experiments are also conducted with the aim of ascertaining the accuracy of the two schemes when integrations are made over long time intervals.     

Countertransference issues in crisis work with natural disaster victims.

Effects of trauma work on mental health workers and intervention methods were studied in a group of American mental health professionals who volunteered to provide crisis intervention and a group of Armenian counselors-in-training who were themselves victims of the catastrophic 1988 earthquake in Soviet Armenia. American clinicians' reactions were addressed through psychodynamic peer support group meetings, while a didactic experiential group instruction program resulted in changes in the posttraumatic stress disorder (PTSD) and depression symptoms of indigenous counselors. Issues related to intergenerational trauma, seeing self as victim, repetition compulsion, and assigned roles in the therapeutic relationship are addressed. Benefits of group process in trauma work, training issues, and implications for future research are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Protective behavioral strategies and the relationship between depressive symptoms and alcohol-related negative consequences among college students.

Approximately 40% of college students reported engaging in heavy episodic or "binge" drinking in the 2 weeks prior to being surveyed. Research indicates that college students suffering from depression are more likely to report experiencing negative consequences related to their drinking than other students are. The reasons for this relationship have not been well-studied. Hence, the purpose of this study was to determine whether use of protective behavioral strategies (PBS), defined as cognitive-behavioral strategies an individual can use when drinking alcohol that limit both consumption and alcohol-related problems, mediated the relationship between depressive symptoms and alcohol-related negative consequences among college students. Data were obtained from 686 participants from a large, public university who were referred to an alcohol intervention as a result of violating on-campus alcohol policies. Results from structural equation modeling analyses indicated that use of PBS partially mediated the relationship between depressive symptoms and alcohol-related negative consequences. Implications for clinicians treating college students who report experiencing depressive symptoms or consuming alcohol are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Two-Level Non-Overlapping Schwarz Preconditioners for a Discontinuous Galerkin Approximation of the Biharmonic Equation

We present some two-level non-overlapping additive and multiplicative Schwarz methods for a discontinuous Galerkin method for solving the biharmonic equation. We show that the condition numbers of the preconditioned systems are of the order O( H ³/h ³) for the non-overlapping Schwarz methods, where h and H stand for the fine mesh size and the coarse mesh size, respectively. The analysis requires establishing an interpolation result for Sobolev norms and Poincaré–Friedrichs type inequalities for totally discontinuous piecewise polynomial functions. It also requires showing some approximation properties of the multilevel hierarchy of discontinuous Galerkin finite element spaces.This revised version was published online in July 2005 with corrected volume and issue numbers.     

A new deformable model for analysis of X-ray CT images in preclinical studies of mice for polycystic kidney disease

This paper describes the application of a new probabilistic shape and appearance model (PSAM) algorithm to the task of detecting polycystic kidney disease (PKD) in X-ray computed tomography images of laboratory mice. The genetically engineered PKD mouse is a valuable animal model that can be used to develop new treatments for kidney-related problems in humans. PSAM is a statistical-based deformable model that improves upon existing point distribution models for boundary-based object segmentation. This new deformable model algorithm finds the optimal boundary position using an objective function that has several unique characteristics. Most importantly, the objective function includes both global shape and local gray-level characteristics, so optimization occurs with respect to both pieces of information simultaneously. PSAM is employed to segment the mouse kidneys and then texture measurements are applied within kidney boundaries to detect PKD. The challenges associated with the segmentation non-rigid organs along with the availability of a priori information led to the choice of a trainable, deformable model for this application. In 103 kidney images that were analyzed as part of a preclinical animal study, the mouse kidneys and spine were segmented with an average error of 2.4 pixels per boundary point. In all 103 cases, the kidneys were successfully segmented at a level where PKD could be detected using mean-of-local-variance texture measurements within the located boundary.     

Recombination-induced random walk diffusion of interstitial carbon in silicon

Recombination events at interstitial carbon atoms in silicon cause the carbon to step to adjacent interstitial positions. DLTS inp-type silicon is used to measure the random walk from interstitial carbon to interstitial carbon-oxygen centers. Electron capture at the interstitial carbon defect causes the carbon to step with a frequency of once per 16 capture events. Using 100 keV electron irradiations to produce electron-hole recombination events, we measure: the step frequency, electron capture cross section, and the mean time between electron captures at the interstitial carbon defect. Measurement of athermal diffusion in the dark indicates that the time between recombination events at interstitial carbon is 0.92 × 10¹¹ seconds if the electron density is 1 m⁻³. Interstitial carbon moves rapidly at low temperature by this random walk in p-type silicon.     

Audience effects on alarm calling in chickens (Gallus gallus).

The male domestic chicken (Gallus gallus) has been found to modulate the production of vocal signals in response to the presence or absence of a suitable audience. We investigated effects on alarm calling by presenting overhead predator models to cockerels in the presence of a variety of social companions. The production of aerial predator calls in response to hawk silhouettes varied with the presence or absence of a member of the same species. The kinds of audience investigated included the mate, unfamiliar females, other females and males with which subjects had had prior visual and auditory contact, and broody hens with and without young. Domestic chicks, unrelated to the subjects, were almost as effective an audience as conspecific adults. A member of another species, however, failed to potentiate alarm-call production. The subjects gave more alarm calls when they were in the presence of either a male or a female audience than when they were alone. By manipulating the visibility of overhead predator models to the subjects and to the audience, we showed that the subjects were not cued by alarm and escape behaviors of the audience. Comparisons with food calling indicate that, in deciding whether to emit a signal in response to the appropriate referent (e.g., food or predators), chickens respond to subtle differences in the nature of the audience with behaviors that vary from one communicative context to another. (PsycINFO Database Record (c) 2010 APA, all rights reserved)