Humidity Dependence of the Fatigue of High-Strength Fused Silica Optical Fibers

Strength and dynamic fatigue behavior of silica fibers has been measured as a function of ambient humidity. Bare and polymer-coated fibers were compared to determine the influence of the coating. The results verify earlier work that suggests the degradation reaction is approximately second order with respect to humidity. However, we verify this result using rigorous data analysis techniques and, unlike the earlier work, the result is shown to be independent of the form of the kinetic model for crack growth. Trends in the calculated fatigue parameters illustrate that a simple exponential crack growth law best describes the humidity data. No significant differences were found between coated and bare fibers, provided the coated fibers were properly equilibrated. A data analysis methodology is given for obtaining valid reaction orders independently of the crack growth law form.     

Influence of chemical and physical characteristics of cement kiln dusts (CKDs) on their hydration behavior and potential suitability for soil stabilization

The interaction of CKDs with a given soil depends on the chemical and physical characteristics of the CKDs. Hence, the characterization of CKDs and their hydration products may lead to better understanding of their suitability as soil stabilizers. In the present article, four different CKD powders are characterized and their hydration products are evaluated. A detailed chemical (X-ray diffraction), thermogravimetric and morphological (scanning electron microscope) analyses of both the CKD powders and the hydrated CKD pastes are presented. In general, high free-lime content (~ 14–29%) CKDs, when reacted with water produced significant amounts of calcium hydroxide, ettringite and syngenite. These CKDs also developed higher unconfined compressive strength and higher temperature of hydration compared to CKDs with lower amounts of free-lime. An attempt was made to qualitatively correlate the performance of CKD pastes with the chemical and physical characteristics of the original CKD powders and to determine their potential suitability as soil stabilizers. To that effect a limited unconfined compressive strength testing of CKD-treated kaolinite clays was performed. The results of this study suggest that both the compressive strength and the temperature of hydration of the CKD paste can give early indications of the suitability of particular CKD for soil stabilization.     

Gender differences in mathematics performance: A meta-analysis.

Performed a meta-analysis of 100 studies (published 1963–1988) of gender differences in mathematics performance. They yielded 254 independent effect sizes, representing the testing of 3,175,188 Ss. Averaged overall effect sizes based on samples of the general population indicated that females outperformed males by only a negligible amount. An examination of age trends indicated that girls showed a slight superiority in computation in elementary school and middle school. There were no gender differences in problem solving in elementary or middle school; differences favoring men emerged in high school and college. Gender differences were smallest and actually favored females in samples of the general population, grew larger with increasingly selective samples, and were largest for highly selected samples and samples of highly precocious persons. The magnitude of the gender difference has declined over the years. Gender differences in mathematics performance are small. Nonetheless, the lower performance of women in problem solving that is evident in high school requires attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Retaliation against whistle blowers: Predictors and effects.

Examined the power–dependency relationships between "whistle blowers" and their employers through the regression analyses of survey data from 636 employees of federal agencies who had reported evidence of official wrongdoing. Ss reported that they were more likely to suffer retaliation if they lacked the support of their supervisors and managers. Retaliation was also more severe if the wrongdoing was serious and if the S used channels outside the organization to report the incident. Following severe retaliation, Ss were likely to file official complaints about the retaliation and to leave their jobs involuntarily. Other predictors of reactions to retaliatory action are discussed. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Screening catalytic lipase activities with an analytical supercritical fluid extractor

Two different screenings of several commercial lipases were performed to find a lipase with superior performance for the conversion of lipid moieties to their fatty acid methyl ester (FAME) derivatives under supercritical conditions. The first screening was done under hydrolytic conditions in a buffer. The second screening was done under supercritical conditions with CO₂, utilizing some of the same lipases for the methanolysis of different lipids. For the substrates studied, there was a significant difference in lipase activity under the two above conditions. Significant hydrolytic activity was demonstrated for three different lipid types (triglycerides, sterols, and phospholipids) with Lipase PS30, but when the same lipase was immobilized on an Accurel carrier (polypropylene), the activity decreased considerably. The opposite was found for Lipase G, which showed strong activity when immobilized and under supercritical conditions. Furthermore, Chirozyme L-1 was superior under supercritical conditions. The altered substrate specificity that some of these lipases show in supercritical CO₂ suggests several interesting synthetic options and applications under these conditions.     

Adult age differences in short-term memory for serial order: Data and a model.

Age-related deficits in short-term memory have been widely reported, but reduced overall scores could reflect increased order errors, increased omissions, or increased intrusions. Different explanations for reduced short-term memory with aging lead to different predictions. In this study, young (n?=?68; M age?=?20 years) and older (n?=?99; M age?=?65 years) adults were presented with lists of letters and were asked to recall each list immediately in the correct order. Age differences in error patterns were similar for auditory and visual presentation. For example, older adults made more errors of every type, and a greater proportion of the older adults' errors were omissions. An additional condition, in which older adults were encouraged to guess, ruled out an age increase in response threshold as a full explanation for the results. The data were modeled by an oscillator-based computational model of memory for serial order. A good fit to the aging data was achieved by simultaneously altering two parameters that were interpreted as corresponding to frontal decline and response slowing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A longitudinal study of the relation between language and theory-of-mind development.

Fifty-nine 3-year-olds were tested 3 times over a period of 7 months in order to assess the contribution of theory of mind to language development and of language to theory-of-mind development (including the independent contributions of syntax and semantics). Language competence was assessed with a standardized measure of reception and production of syntax and semantics (the Test of Early Language Development). Theory of mind was assessed with false-belief tasks and appearance–reality tasks. Earlier language abilities predicted later theory-of-mind test performance (controlling for earlier theory of mind), but earlier theory of mind did not predict later language test performance (controlling for earlier language). These findings are consistent with the argument that language is fundamental to theory-of mind development. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adult age comparisons in the processing of event frequency information.

The usual superiority in frequency-of-occurrence judgments of younger vs older subjects was hypothesized to result from greater strategic encoding of the materials conveying frequency information. A subject-paced, visual search task was designed to control nontarget word encoding. Relative frequency judgments for the nontarget word pairs were equally accurate for younger and older subjects, and performance of both groups was above chance. Results suggest that strategic cover-task encoding can induce age differences in incidental frequency processing. Consistent with a nonoptimal as opposed to an optimal view, automatic processes require only minimal capacity for above-chance performance, but additional strategic resources can increase performance. When such additional resources are used more by younger than by older subjects, the former are better in frequency performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)