Relations among conceptual knowledge, procedural knowledge, and procedural flexibility in two samples differing in prior knowledge.

Competence in many domains rests on children developing conceptual and procedural knowledge, as well as procedural flexibility. However, research on the developmental relations between these different types of knowledge has yielded unclear results, in part because little attention has been paid to the validity of the measures or to the effects of prior knowledge on the relations. To overcome these problems, we modeled the three constructs in the domain of equation solving as latent factors and tested (a) whether the predictive relations between conceptual and procedural knowledge were bidirectional, (b) whether these interrelations were moderated by prior knowledge, and (c) how both constructs contributed to procedural flexibility. We analyzed data from 2 measurement points each from two samples (Ns = 228 and 304) of middle school students who differed in prior knowledge. Conceptual and procedural knowledge had stable bidirectional relations that were not moderated by prior knowledge. Both kinds of knowledge contributed independently to procedural flexibility. The results demonstrate how changes in complex knowledge structures contribute to competence development. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Automatic associations and panic disorder: Trajectories of change over the course of treatment.

Cognitive models of anxiety and panic suggest that symptom reduction during treatment should be preceded by changes in cognitive processing, including modifying the anxious schema. The current study tested these hypotheses by using a repeated measures design to evaluate whether the trajectory of change in automatic panic associations over a 12-week course of cognitive behavior therapy (CBT) is related to the trajectory of change in panic symptoms. Individuals with panic disorder (N = 43) completed a measure of automatic panic associations--the Implicit Association Test (A. G. Greenwald, D. E. McGhee, & J. L. K. Schwartz, 1998), which reflects elements of the schema construct--every 3 weeks over the course of therapy and measures of panic symptoms each week. Dynamic bivariate latent difference score modeling not only indicated that automatic panic associations changed over the course of CBT for panic disorder but showed these changes were correlated with symptom reduction. Moreover, change in automatic panic associations was a significant predictor of change in panic symptom severity. These findings permit inferences about the temporality of change, suggesting that cognitive change does in fact precede and contribute to symptom change. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Behavioral economic analysis of natural resolution of drinking problems using IVR self-monitoring.

This study investigated whether a behavioral economic index of the value of rewards available over different time horizons predicted patterns of alcohol consumption shortly after natural resolution when the risk of relapse is high. Using a computerized interactive voice response (IVR) telephone system, untreated problem drinkers (n = 41) self-monitored their daily drinking, monetary expenditures, and surrounding contexts over intervals that ranged from a maximum of 42 to 128 days. Expanded Timeline Followback interviews were conducted before and after the IVR interval and 1 year after the baseline assessment. Stable resolutions generally and moderation resolutions specifically were associated with proportionally more preresolution expenditures on savings and less on alcohol compared to heavy drinking outcomes. The findings replicated and extended earlier research and suggested that the extent to which problem drinkers organized their behavior over longer intervals, even when drinking abusively, helped identify who resolved, including who transitioned to stable moderation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dendrimer templates for heterogeneous catalysts: Bimetallic Pt–Au nanoparticles on oxide supports

Polyamidoamine (PAMAM) dendrimers were used to template Pt, Au, and bimetallic Pt–Au dendrimer encapsulated nanoparticles (DENs) in solution. Adjusting the solution pH allowed for slow, spontaneous adsorption of the nanoparticles onto silica, alumina, and titania. After dendrimer removal, the catalysts were characterized with infrared spectroscopy of adsorbed CO and tested with CO oxidation catalysis. Infrared spectroscopy of the monometallic Pt catalysts showed a slight shift in the CO stretching frequency for the different supports. For the bimetallic catalysts, infrared spectra showed CO adsorbed on both Pt and on Au sites. Spectra collected during CO desorption showed substantial interactions between the two bands, confirming the presence of bimetallic particles on all the supports. The bimetallic catalysts were found to be more active than the monometallic catalysts and had lower apparent activation energies. The titania supported Pt–Au catalyst was resistant to deactivation during an extended treatment at 300 °C. Correlations between IR spectra and catalytic activity showed differences between the mono- and bimetallic materials and implicated a bimetallic Pt–Au ensemble at the catalytic active site. This is the first study to show that DENs are appropriate precursors for studying support effects on catalysis by metal nanoparticles, although the magnitude of the effects were small.     

In-roads to the spread of antibiotic resistance: regional patterns of microbial transmission in northern coastal Ecuador

The evolution of antibiotic resistance (AR) increases treatment cost and probability of failure, threatening human health worldwide. The relative importance of individual antibiotic use, environmental transmission and rates of introduction of resistant bacteria in explaining community AR patterns is poorly understood. Evaluating their relative importance requires studying a region where they vary. The construction of a new road in a previously roadless area of northern coastal Ecuador provides a valuable natural experiment to study how changes in the social and natural environment affect the epidemiology of resistant Escherichia coli. We conducted seven bi-annual 15 day surveys of AR between 2003 and 2008 in 21 villages. Resistance to both ampicillin and sulphamethoxazole was the most frequently observed profile, based on antibiogram tests of seven antibiotics from 2210 samples. The prevalence of enteric bacteria with this resistance pair in the less remote communities was 80 per cent higher than in more remote communities (OR = 1.8 [1.3, 2.3]). This pattern could not be explained with data on individual antibiotic use. We used a transmission model to help explain this observed discrepancy. The model analysis suggests that both transmission and the rate of introduction of resistant bacteria into communities may contribute to the observed regional scale AR patterns, and that village-level antibiotic use rate determines which of these two factors predominate. While usually conceived as a main effect on individual risk, antibiotic use rate is revealed in this analysis as an effect modifier with regard to community-level risk of resistance.