Access to Print in Low‐Income and Middle‐Income Communities: An Ecological Study of Four Neighborhoods

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/88026/1/RRQ.36.1.1.pd

Mesoscopic models for DNA stretching under force: new results and comparison to experiments

Single molecule experiments on B-DNA stretching have revealed one or two structural transitions, when increasing the external force. They are characterized by a sudden increase of DNA contour length and a decrease of the bending rigidity. It has been proposed that the first transition, at forces of 60--80 pN, is a transition from B to S-DNA, viewed as a stretched duplex DNA, while the second one, at stronger forces, is a strand peeling resulting in single stranded DNAs (ssDNA), similar to thermal denaturation. But due to experimental conditions these two transitions can overlap, for instance for poly(dA-dT). We derive analytical formula using a coupled discrete worm like chain-Ising model. Our model takes into account bending rigidity, discreteness of the chain, linear and non-linear (for ssDNA) bond stretching. In the limit of zero force, this model simplifies into a coupled model already developed by us for studying thermal DNA melting, establishing a connexion with previous fitting parameter values for denaturation profiles. We find that: (i) ssDNA is fitted, using an analytical formula, over a nanoNewton range with only three free parameters, the contour length, the bending modulus and the monomer size; (ii) a surprisingly good fit on this force range is possible only by choosing a monomer size of 0.2 nm, almost 4 times smaller than the ssDNA nucleobase length; (iii) mesoscopic models are not able to fit B to ssDNA (or S to ss) transitions; (iv) an analytical formula for fitting B to S transitions is derived in the strong force approximation and for long DNAs, which is in excellent agreement with exact transfer matrix calculations; (v) this formula fits perfectly well poly(dG-dC) and $\lambda$-DNA force-extension curves with consistent parameter values; (vi) a coherent picture, where S to ssDNA transitions are much more sensitive to base-pair sequence than the B to S one, emerges.Comment: 14 pages, 9 figure

Sharing information books with kindergartners: The role of parents’ extra-textual talk and socioeconomic status

The purpose of the study was to explore how features of parent-child extra-textual talk during information book-sharing might vary across different socioeconomic backgrounds, and to determine if certain interactional patterns might mediate their effects on children's receptive and expressive vocabulary development. Sixty parents and their 5-year-old children were audio-recorded reading an unfamiliar information book in their home. Holistic coding on six parent and two child engagement scales, examining low to high cognitive demanding talk was conducted. Results indicated that lexical richness and contingent responsiveness positively predicted receptive and expressive vocabulary. Further, contingent responsiveness appeared to mediate the influence of socioeconomic status on children's receptive and expressive vocabulary, suggesting that positive environmental contexts and supportive parent-child interactions can have a powerful influence on children's development

From ABCs to DVDs: Profiles of infants' home media environments in the first two years of life

The very definition of print exposure has evolved in recent years as has the production of new media for infants and toddlers. Recognising that parents now have a confluence of media to select from, our study was designed to provide a richer understanding of home-literacy environments among 100 infants. Three profiles of families' home media environments emerged: (1) media abstainers, who neither knew much about baby books and DVDs nor owned them; (2) media knowers, who knew about baby books and DVDs, but chose to own many books and hardly any DVDs; and (3) media owners, who owned many baby books and DVDs, but appeared to have little knowledge about them. Parents who were readers themselves owned more baby books but fewer baby DVDs than parents with less print exposure. Results suggest a more complex understanding of print exposure in home environments than previously understood. © 2013 Taylor & Francis