Evaluating the accuracy of a three-term pencil beam algorithm in heterogeneous media.

The goal of this work was to evaluate the accuracy of our in-house analytical dose calculation code against MCNPX data in heterogeneous phantoms. The analytical model utilizes a pencil beam model based on Fermi-Eyges theory to account for multiple Coulomb scattering and a least-squares fit to Monte Carlo data to account for nonelastic nuclear interactions as well as any remaining, uncharacterized scatter (the 'nuclear halo'). The model characterized dose accurately (up to 1% of maximum dose in broad fields (4 × 4 cm2 and 10 × 10 cm2) and up to 0.01% in a narrow field (0.1 × 0.1 cm2) fit to MCNPX data). The accuracy of the model was benchmarked in three types of stylized phantoms: (1) homogeneous, (2) laterally infinite slab heterogeneities, and (3) laterally finite slab heterogeneities. Results from homogeneous phantoms and laterally infinite slab heterogeneities showed high levels of accuracy (>98% of points within 2% or 0.1 cm distance-to-agreement (DTA)). However, because range straggling and secondary particle production were not included in our model, central-axis dose differences of 2-4% were observed in laterally infinite slab heterogeneities when compared to Monte Carlo dose. In the presence of laterally finite slab heterogeneities, the analytical model resulted in lower pass rates (>96% of points within 2% or 0.1 cm DTA), which was attributed to the use of the central-axis approximation.

Content and Perceived Utility of Mental Imagery by Older Adults in a Peer-Delivered Physical Activity Intervention.

Imagery interventions intended to increase exercise behavior are rare. The Active Adult Mentoring Program (AAMP) was a randomized controlled trial with imagery content. The purposes of this study were to examine the content and perceived utility of mental imagery with 24 AAMP participants (Mage = 65.00, SD = 8.79 years). Digital recordings of AAMP sessions and post-intervention interviews were content-analyzed. Emergent themes included images of the physical activity context and negative impressions about imagery. Post-intervention interviews revealed that 13 participants reported positive experiences using mental imagery while 9 would not engage in further use. Important implications are discussed.

Evaluation of the toxicity of concentrated barley beta-glucan in a 28-day feeding study in Wistar rats.

Beta-glucans are water-soluble cell-wall polysaccharides consisting of (1-->3,1-->4)-linked beta-D-glucopyranosyl monomers that comprise a considerable proportion of soluble fiber from certain grains including oats and barley. Consumption of foods containing beta-glucan or beta-glucan-enriched fractions prepared from these grains lower serum cholesterol concentrations in humans and in animal models of hypercholesterolemia. The present study was conducted to evaluate the toxicity of beta-glucan-enriched soluble fiber from barley in Wistar rats on dietary administration at concentrations of 0.7, 3.5 and 7% beta-glucan for 28 days. There were no adverse effects on general condition and behavior, growth, feed and water consumption, feed conversion efficiency, red blood cell and clotting potential parameters, clinical chemistry values, and organ weights. Necropsy and histopathology findings revealed no treatment-related changes in any organ evaluated. A dose-dependent increase in full and empty cecum weight was observed. This is a common physiological response of rodents to high amounts of poorly digestible, fermentable carbohydrates, and was of no toxicological concern. The only finding of possible biological relevance was an increase in the number of circulating lymphocytes observed in males. However, the increase was not dose-dependent and was not observed in females. Results of this study demonstrated that consumption of concentrated barley beta-glucan was not associated with any obvious signs of toxicity in Wistar rats even following consumption of large quantities.

Hyperactive and antisocial behaviors: comorbid or two points in the same process?

We hypothesized that hyperactivity defines the first stage and that antisocial problems define a second stage in a progression that leads eventually to early-onset delinquency. As expected, a structural equation model (SEM) showed that a latent construct for hyperactivity was significantly related to a latent construct for antisocial problems. We hypothesized that this path reflected a shared mechanism, disrupted parental discipline. A second SEM showed that the relation between hyperactivity and antisocial behavior really reflected a shared disruption in parental discipline. A third SEM showed that having antisocial parents was uniquely correlated with antisocial children but not with hyperactivity. A fourth SEM showed that early-onset delinquency was predicted by a latent construct for antisocial child; but when this was partialed out, the contribution for hyperactivity was nonsignificant.

Neuroimaging findings in twins discordant for Alzheimer's disease.

Data from computed tomography (CT) scans of 12 twin pairs in which one partner had Azheimer's disease (AD) and the other partner is cognitively intact were analyzed to study structural brain features associated with AD while controlling for familial factors. Visual ratings and analysis of quantified areas and volumes indicated that AD twins showed more dilation of temporal horns, lateral ventricles and third ventricle, and more atrophy of temporal lobes, particularly in the anterior temporal/perisylvian area, than their healthy cotwins. Demented twins did not have smaller intracranial areas or overall brain volumes than their intact partners. The apolipoprotein sigma-4 allele was associated with greater dilation of lateral ventricles and ventricular volume. Significant intrapair correlations were found for total intracranial area and volume, cerebellar area and white matter lesions.

Endoscopic cultures of the proximal gastrointestinal tract.

The purpose of this study was to evaluate two methods of obtaining culture material under direct visualization through a fiberoptic upper gastrointestinal endoscope. Collections were made both with a wash pipe and a sterile brush through a sterilized Olympus D panendoscope. Paired aspirate collections were made on 20 occasions from 10 postgastrectomy and six nonoperated patients. Significant bacterial overgrowth was identified equally well by both methods, the the wash tube, which can be reused, is cheaper. The endoscopic method for collecting proximal fluid for culture is simple and can be performed during a routine endoscopy.