Thermal properties of poly(pivalolactone)

Polypivalolactone (PPVL) is a highly crystalline polyester formed either by nucleophilic or electrophilic ring-opening polymerization of 2,2-dimethyl-β-propiolactone, commonly known as pivalolactone (PVL). The thermal properties and crystallization kinetics of the polymer formed under reaction injection molding (RIM) conditions were studied. The crystallization kinetics of PPVL were measured using differential scanning calorimetry (DSC), and Avrami theory was used to interpret the bulk crystallization kinetics. A comparison was made with commercially prepared PPVL. The kinetics data indicate laboratory prepared PPVL, which is of lower molecular weight, has similar crystallization rates compared to the higher molecular weight commercial material. The kinetics data also indicate the rate of crystallization is relatively rapid overall for PPVL, with low activation energies of crystallization. The calorimetric studies also utilized DSC and simultaneous ther-mogravimetric analysis/differential scanning calorimetry (TGA/DSC). Thermal analysis showed a clear difference in melting behavior between high and low molecular weight material, possibly a reflection of the presence of the α and γ-crystal forms of the polymer.     

Mirror use by African Grey parrots (Psittacus erithacus).

Two Grey parrots (Psittacus erithacus) were tested on various types of mirror use: mirror image stimulation, mirror-mediated object discrimination, and a simple form of mirror-mediated spatial locating. During exposure to a mirror, neither bird clearly demonstrated self-exploratory behavior but responded instead in ways similar to those of marmosets, monkeys, dolphins, extremely young children (     

Category learning deficits in Parkinson's disease.

Sixteen patients with Parkinson's disease (PD), 15 older controls (OCs), and 109 younger controls (YCs) were compared in 2 category-learning tasks. Participants attempted to assign colored geometric figures to 1 of 2 categories. In rule-based tasks, category membership was defined by an explicit rule that was easy to verbalize, whereas in information-integration tasks, there was no salient verbal rule and accuracy was maximized only if information from 3 stimulus components was integrated at some predecisional stage. The YCs performed the best on both tasks. The PD patients were highly impaired compared with the OCs, in the rule-based categorization task but were not different from the OCs in the information-integration task. These results support the hypothesis that learning in these 2 tasks is mediated by functionally separate systems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Use and maintenance of strategies: The influence of accessibility to knowledge.

Conducted 2 experiments in which the interaction between strategy use and accessibility to relevant knowledge was investigated. Ss were asked to memorize a list of categorizable words, and use of a categorization strategy was assessed. Typicality of the category exemplars was varied in a between-Ss fashion to manipulate accessibility to relevant knowledge and the S's experience with the strategy. Ss were then given a 2nd list of categorizable words to memorize, and the use of a categorization strategy was again assessed. In Exp 2, attributional data regarding strategy use were also collected. Results from the 2 experiments show that variations in accessibility to knowledge have a significant effect on strategy use on the 1st memorization trial. Experiencing highly typical items on the 1st list was found to be associated with continued use of the strategy on the 2nd list (i.e., ease of use on the 1st trial affected maintenance of the strategy). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Automatic crack growth prediction in rails with BEM

Durability and damage tolerance calculations are typically based on experimental data or analytical studies of simplified cases. In this paper, a new numerical approach is described which can be used with the full model loading to compute the stress intensity factors and also to automatically predict how cracks will propagate.The benefits of the full numerical computation of the stress field are numerous, accurate prediction of crack growth, improved stress intensity data and more accurate prediction of life, thus providing an accurate method for the forensic analysis of failures.The crack growth process can be modelled with a variety of crack growth models relating the rate of crack growth to the computed stress intensity factors. The crack growth itself can include the effects of multiple load cases including the effect of residual stress fields.The crack growth process itself is fully automated by automatically re-meshing the crack surface and the nearby surfaces of the structure. The crack growth process is aided by the use of a fracture wizard that enables the necessary components for the analysis to be selected and the analysis to be controlled.Applications will be presented describing the potential applications of the method to the growth of cracks in rail components.     

Effects of reciprocal peer tutoring on academic achievement and psychological adjustment: A component analysis.

A component analysis of the reciprocal peer tutoring (RPT) strategy was performed, which previous research had demonstrated to be effective in producing cognitive gains, lowering subjective distress, and enhancing course satisfaction. One hundred students were randomly assigned to one of four groups designed to systematically compare the RPT strategy with its hypothesized components: dyadic, mutual exchange, and structured-learning format. Pretest analyses revealed no significant group differences in demographic variables or pretest scores on course examinations and self-report inventories of subjective distress. Further analyses supported past findings on the superiority of the RPT strategy. This superiority was attributed to the RPT group's unique combination of elements: preparing to teach a peer teaching a peer, and accountability for this process. We discuss implications for future research. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Partner unsupportive responses, avoidant coping, and distress among women with early stage breast cancer: Patient and partner perspectives.

This 18-month longitudinal study examined the associations among partner unsupportive behavior, avoidant coping, and distress experienced by 219 women with early stage breast cancer. The role of patient and partner ratings of unsupportive behavior were evaluated. Results indicated that patient and partner ratings of unsupportive behavior were highly correlated. Growth curve modeling suggested that unsupportive behavior, from both patient and partner perspectives, predicted more avoidant coping and distress. When partner and patient perceptions were placed in the same model, patient perceptions mediated the association between partners' ratings of their unsupportive behavior and patient distress. Avoidance also mediated the association between unsupportive behavior and distress, extending prior cross-sectional findings. Results highlight the long-term detrimental effects of partners' unsupportive behavior on the quality of life of women with early stage breast cancer. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Selective processing of threat cues in posttraumatic stress disorder.

Vietnam combat veterans with (n?=?15) and without (n?=?15) posttraumatic stress disorder (PTSD) performed a modified Stroop task in which they named the colors of neutral words (e.g., INPUT), positive words (e.g., LOVE), obsessive-compulsive disorder (OCD) words (e.g., GERMS), and PTSD words (e.g., BODYBAGS). In contrast to normal controls, PTSD patients took significantly longer to color-name PTSD words than to color-name neutral, OCD, and positive words. Because Stroop interference reflects involuntary semantic activation, it may provide a quantitative measure of intrusive cognitive activity, the hallmark symptom of PTSD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)