Gene-environment interactions across development: Exploring DRD2 genotype and prenatal smoking effects on self-regulation.

Genetic factors dynamically interact with both pre- and postnatal environmental influences to shape development. Considerable attention has been devoted to gene-environment interactions (G × E) on important outcomes (A. Caspi & T. E. Moffitt, 2006). It is also important to consider the possibility that these G × E effects may vary across development, particularly for constructs like self-regulation that emerge slowly, depend on brain regions that change qualitatively in different developmental periods, and thus may be manifested differently. To illustrate one approach to exploring such developmental patterns, the relation between variation in the TaqIA polymorphism, related to D2 dopamine receptor expression and availability, and prenatal exposure to tobacco was examined in two exploratory studies. First, in 4-week-old neonates, genotype-exposure interactions were observed for attention and irritable reactivity, but not for stress dysregulation. Second, in preschool children, genotype was related to Preschool Trail Making Test (K. A. Espy and M. F. Cwik, 2004) task performance on conditions requiring executive control; children with both the A1+ genotype and a history of prenatal tobacco exposure displayed disproportionately poor performance. Despite study limitations, these results illustrate the importance of examining the interplay between genetic and prenatal environmental factors across development. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Using confirmatory factor analysis to understand executive control in preschool children: I. Latent structure.

Although many tasks have been developed recently to study executive control in the preschool years, the constructs that underlie performance on these tasks are poorly understood. In particular, it is unclear whether executive control is composed of multiple, separable cognitive abilities (e.g., inhibition and working memory) or whether it is unitary in nature. A sample of 243 normally developing children between 2.3 and 6 years of age completed a battery of age-appropriate executive control tasks. Confirmatory factor analysis was used to compare multiple models of executive control empirically. A single-factor, general model was sufficient to account for the data. Furthermore, the fit of the unitary model was invariant across subgroups of children divided by socioeconomic status or sex. Girls displayed a higher level of latent executive control than boys, and children of higher and lower socioeconomic status did not differ in level. In typically developing preschool children, tasks conceptualized as indexes of working memory and inhibitory control in fact measured a single cognitive ability, despite surface differences between task characteristics. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Theoretical and experimental study of the molten polymer flow in the calender bank

The flow of molten polymers in the calender bank has been computed using a finite-element method with stream function and vorticity. Two nonsymmetrical-recirculating regions have been obtained fully in agreement with the experimental observations on poly(vinyl chloride) melt banks. The pressure distribution along the flow axis is very close to the one obtained using the classical-lubrication approximation.     

Prenatal tobacco exposure: Developmental outcomes in the neonatal period.

Smoking during pregnancy is a persistent public health problem that has been linked to later adverse outcomes. The neonatal period—the first month of life—carries substantial developmental change in regulatory skills and is the period when tobacco metabolites are cleared physiologically. Studies to date mostly have used cross-sectional designs that limit characterizing potential impacts of prenatal tobacco exposure on the development of key self-regulatory processes and cannot disentangle short-term withdrawal effects from residual exposure-related impacts. In this study, pregnant participants (N = 304) were recruited prospectively during pregnancy, and smoking was measured at multiple time points, with both self-report and biochemical measures. Neonatal attention, irritable reactivity, and stress dysregulation were examined longitudinally at three time points during the first month of life, and physical growth indices were measured at birth. Tobacco-exposed infants showed significantly poorer attention skills after birth, and the magnitude of the difference between exposed and nonexposed groups attenuated across the neonatal period. In contrast, exposure-related differences in irritable reactivity largely were not evident across the 1st month of life, differing marginally at 4 weeks of age only. Third-trimester smoking was associated with pervasive, deleterious, dose–response impacts on physical growth measured at birth, whereas nearly all smoking indicators throughout pregnancy predicted level and growth rates of early attention. The observed neonatal pattern is consistent with the neurobiology of tobacco on the developing nervous system and fits with developmental vulnerabilities observed later in life. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Alkylaluminum–Lewis base complexes as initiators of vinyl polymerization

Complexes of aluminum alkyls with Lewis bases catalyze the polymerization of vinyl chloride. Triethylaluminum is most effective, but other compounds of type R₃Al, R₂AlCl, R₂AlH, and LiAIR₄ are operable. Dialkylmagnesiums are active, but Grignard reagents, as well as a number of other metal alkyls are inactive. Among Lewis bases, tetrahydrofuran (THF) and tetrahydropyran give the best yields of poly(vinyl chloride). Oxygen bases, such as ethers and esters, are more effective than nitrogen bases, e.g., tertiary amines. Cyclic compounds are better than acyclic ones. The polymerization occurs in a variety of hydrocarbon, chlorinated hydrocarbon, or ether solvents, but especially well in CCl₄. Radical polymerization is probably initiated through the reaction R₃Al:Base + CCl₄ → R₂AlCl: Base + R + Cl₃C., to form trichloromethyl radical.     

Growth mixture modeling of academic achievement in children of varying birth weight risk.

The extremes of birth weight and preterm birth are known to result in a host of adverse outcomes, yet studies to date largely have used cross-sectional designs and variable-centered methods to understand long-term sequelae. Growth mixture modeling (GMM) that utilizes an integrated person- and variable-centered approach was applied to identify latent classes of achievement from a cohort of school-age children born at varying birth weights. GMM analyses revealed 2 latent achievement classes for calculation, problem-solving, and decoding abilities. The classes differed substantively and persistently in proficiency and in growth trajectories. Birth weight was a robust predictor of class membership for the 2 mathematics achievement outcomes and a marginal predictor of class membership for decoding. Neither visuospatial-motor skills nor environmental risk at study entry added to class prediction for any of the achievement skills. Among children born preterm, neonatal medical variables predicted class membership uniquely beyond birth weight. More generally, GMM is useful in revealing coherence in the developmental patterns of academic achievement in children of varying weight at birth and is well suited to investigations of sources of heterogeneity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Measuring the development of executive control with the shape school.

Although several neurodevelopmental and psychiatric disorders can emerge during the preschool period, there are comparatively few instruments to assess executive control. Evidence for validity of the Shape School (K. A. Espy, 1997) was examined in a sample of 219 typically developing young children. There was good evidence for validity, as Shape School performance variables were interrelated and were associated to other criterion measures considered to measure aspects of executive control. Also suggesting validity, the Shape School variables varied as a function of whether the task demands (a) were executive, (b) required inhibition of a prepotent response or context-controlled selection among relevant stimulus-response sets, and (c) included unitary or concurrent processing. The Shape School may be an effective tool by which to measure executive control in young children who have atypical developmental patterns. (PsycINFO Database Record (c) 2010 APA, all rights reserved)