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)     

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)     

University professors' views of knowledge and validation processes.

Professors in 6 matched pure and applied fields of study were interviewed to determine the validation processes and truth criteria used in their disciplines. Differences across disciplines were found in the validation processes and in the importance placed on conceptual frameworks or models. Use of empirical evidence was more important in the natural and social sciences; peer review was more important in the humanities. Professors in pure fields of study were more likely to use conflicting evidence or counterexamples in validating their work than were professors in applied fields. The results suggest that different fields of study operate according to different sets of rules. An important part of university instruction is to provide students with a sense of what these rules are and how they affect learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Young adults' immediate and delayed reactions to simulated marital conflicts: Implications for intergenerational patterns of violence in intimate relationships.

This study investigated the thoughts and feelings that young adults from violent (VPA) and nonviolent (NPA) interparental-conflict backgrounds reported while listening to simulated marital conflicts and after a delay for reflection. While listening to conflicts, VPAs were more likely than NPAs to predict negative outcomes and to place blame. No between–groups differences regarding negative outcomes emerged after a delay. VPAs also reported perpetrating and experiencing more aggressive conflict in their dating relationships. Post hoc probes revealed that the negative-outcome-prediction and blaming variables played no significant mediating role in participants' intergenerational patterns of intimate-relationship aggression; however, methodological limitations likely compromised the statistical power for examining this mediational model. Results are discussed in light of research regarding intergenerational patterns of violence within families. (PsycINFO Database Record (c) 2010 APA, all rights reserved)