This study examines the role of exposure to speech in children's early vocabulary growth. It is generally assumed that individual differences in vocabulary depend, in large part, on variations in learning capacity. However, variations in exposure have not been systematically explored. In this study we characterize vocabulary growth rates for each of 22 children by using data obtained at several time points from 14 to 26 months. We find a substantial relation between individual differences in vocabulary acquisition and variations in the amount that particular mothers speak to their children. The relation between amount of parent speech and vocabulary growth, we argue, reflects parent effects on the child, rather than child-ability effects on the parent or hereditary factors. We also find that gender is an important factor in rate of vocabulary growth.The work reported here was supported by grants from the Spencer Foundation and the Smart Family Foundation to Janellen Huttenlocher. We thank Peter R. Huttenlocher and James W Stigler for their helpful comments on the manuscript.

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Young gay, bisexual, and other men who have sex with men (MSM) experience sexual health disparities due to a lack of support in settings that traditionally promote positive youth development. The Internet may help to fill this void, but little is known about how it is used for sexual health purposes among young MSM. This mixed-methods study reports quantitative results of a large survey of 18-24 year old MSM in an HIV testing clinic (N = 329) as well as qualitative results from interviews. Level of Internet use was high in this sample and the majority of participants reported using the Internet to find HIV/AIDS information. Black and Latino youth used the Internet less frequently than White youth, and after controlling for age, education, and frequency of Internet use, Black youth were 70% less likely to use the Internet to find HIV/AIDS information. Qualitative analyses identified themes related to the role of the Internet in finding sexual health information, sexual minority identity development, and sexual risk taking behaviors. Participants reported that the Internet filled an important and unmet need for sexual health education. It allowed for connections to the gay community and support during the coming out process, but also exposure to homophobic messages. There was no evidence of increased risk behaviors with partners met online, but at the same time the potential for the use of the Internet to facilitate safer sex communication was largely untapped. Our findings generally present an optimistic picture about the role of the Internet in the development of sexual health among young MSM.

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The importance of ecological management for reducing the vulnerability of biodiversity to climate change is increasingly recognized, yet frameworks to facilitate a structured approach to climate adaptation management are lacking. We developed a conceptual framework that can guide identification of climate change impacts and adaptive management options in a given region or biome. The framework focuses on potential points of early climate change impact, and organizes these along two main axes. First, it recognizes that climate change can act at a range of ecological scales. Secondly, it emphasizes that outcomes are dependent on two potentially interacting and countervailing forces: (1) changes to environmental parameters and ecological processes brought about by climate change, and (2) responses of component systems as determined by attributes of resistance and resilience. Through this structure, the framework draws together a broad range of ecological concepts, with a novel emphasis on attributes of resistance and resilience that can temper the response of species, ecosystems and landscapes to climate change. We applied the framework to the world’s largest remaining Mediterranean-climate woodland, the ‘Great Western Woodlands’ of south-western Australia. In this relatively intact region, maintaining inherent resistance and resilience by preventing anthropogenic degradation is of highest priority and lowest risk. Limited, higher risk options such as fire management, protection of refugia and translocation of adaptive genes may be justifiable under more extreme change, hence our capacity to predict the extent of change strongly impinges on such management decisions. These conclusions may contrast with similar analyses in degraded landscapes, where natural integrity is already compromised, and existing investment in restoration may facilitate experimentation with higher risk options

Observations show that the urban heat island in the atmospheric layer below roof level is most strongly developed during calm, cloudless conditions at night. This paper outlines two versions of a numerical model to describe the cooling of rural and street canyon surfaces under these conditions using surface thermal and radiative properties and the radiative geometry of the canyons. One version uses a full system of differential equations and the other the simpler force-restore approach. The two approaches are shown to be in general agreement and the output of the simpler model is shown to give a faithful representation of cooling of rural and urban surfaces. and therefore heat islands. when compared with field observations.

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Southwestern Australia, with a semiarid Mediterranean climate, has been extensively cleared of native vegetation for winter-growing agricultural species. The resultant reduction in evapotranspiration has increased land salinisation. Through detailed meteorological and vegetation measurements over both agricultural and native vegetation, the bunny fence experiment is addressing the impact on the climate of replacing native perennial vegetation with wintergrowing annual species. Such measurements will give a better understanding of the interaction between the land surface and the atmosphere and are important for improved parameterization of the boundary layer in climate models.