Peer relationships are commonly thought to be critical for adolescent socialization, including the development of negative health behaviors such as alcohol and tobacco use. The interplay between genetic liability and peer influences on the development of adolescent alcohol and tobacco use was examined using a nationally-representative sample of adolescent sibling pairs and their best friends. Genetic factors, some of them related to an adolescent's own substance use and some of them independent of use, were associated with increased exposure to best friends with heavy substance use-a gene-environment correlation. Moreover, adolescents who were genetically liable to substance use were more vulnerable to the adverse influences of their best friends-a geneenvironment interaction. KeywordsGene-environment interaction; Gene-environment correlation; Peer influence; Alcohol use; Adolescence; Substance use Peer relationships are important contexts for adolescent development and socialization (Hartup 1986), including the development of alcohol and tobacco use, two health risk behaviors that are highly comorbid in adolescence (Istvan and Matarazzo 1984) and may share a common genetic etiology (Young et al. 2006). Affiliation with alcohol or tobacco using peers is one of the strongest correlates of adolescents' own use. This observation has led to conclusions about the adverse effects of "peer pressure." There are, however, major difficulties in concluding that resemblance between adolescent peers is indicative of a straightforward causal mechanism (Bauman and Ennett 1996;Kandel 1996).First, adolescents do not randomly choose their friends. Rather, certain factors will increase the likelihood that an adolescent will choose a best friend who uses alcohol and tobacco. Both Cleveland et al. (2005) and Fowler et al. (2007b) found that adolescents' genes influenced their exposure to peers who used alcohol and cigarettes. This process, whereby genetic predispositions affect the likelihood of being exposed to environmental risks, is known as geneenvironment correlation, or rGE (Rutter and Silberg 2002). Moreover, these same genetic factors may also influence adolescents' own use, thus accounting for the resemblance between adolescent peers. This kind of gene-environment correlation has been found to account for the similarity of best friends for smoking and drinking and for serious delinquency in the few extant genetically-informed studies (Hill et al. in press;Rowe et al. 1984 Second, any causal effect of peers may be moderated by characteristics of the adolescent, such that some adolescents are more vulnerable or resilient to peer influence. Self-esteem, insecure attachment style, and previous drinking behavior have been shown to predict individual differences in the magnitude of peer effects (Allen et al. 2006;Duncan et al. 2005;Urberg et al. 2003). One unexplored possibility is that genetic factors related to alcohol and tobacco use may also influence vulnerability to peer influence. This process, whereby genetic pre...

The relation between timing of first sex and later delinquency was examined using a genetically informed sample of 534 same-sex twin pairs from the National Longitudinal Study of Adolescent Health, who were assessed at three time points over a 7-year interval. Genetic and environmental differences between families were found to account for the association between earlier age at first sex and increases in delinquency. After controlling for these genetic and environmental confounds using a quasi-experimental design, earlier age at first sex predicted lower levels of delinquency in early adulthood. The current study is contrasted with previous research with non-genetically informative samples, including Armour and Haynie. Results suggest a more nuanced perspective on the meaning and consequences of adolescent sexuality than is commonly put forth in the literature.

Affiliation with substance using peers is one of the strongest predictors of adolescent alcohol use. This association is typically interpreted causally: peers who drink incite their friends to drink. This association may be complicated by uncontrolled genetic and environmental confounds because teens with familial predispositions for adolescent substance use may be more likely to select into social networks where drinking is common. We test this alternative hypothesis using a sample of 1,820 twin and sibling pairs, and their same-sex best friends, from three waves of the National Longitudinal Study of Adolescent Health. Across all three waves, peer report of substance use did not influence adolescent alcohol use when genetic and shared environmental predispositions for drinking were considered. The association between alcohol use and peer behavior may be a spurious association attributable to a shared genetic liability to drink alcohol and associate with peers who drink alcohol.

The objective of these projects was to investigate alternative technologies for non-fuel uses of coal. Special emphasis was placed on developing premium carbon products from coal-derived feedstocks. A total of 14 projects, which are the 2003 Research Projects, are reported herein. These projects were categorized into three overall objectives. They are:(1) To explore new applications for the use of anthracite in order to improve its marketability; (2) To effectively minimize environmental damage caused by mercury emissions, CO 2 emissions, and coal impounds; and (3) To continue to increase our understanding of coal properties and establish coal usage in non-fuel industries.Research was completed in laboratories throughout the United States. Most research was performed on a bench-scale level with the intent of scaling up if preliminary tests proved successful.These projects resulted in many potential applications for coal-derived feedstocks. These include:• Use of anthracite as a sorbent to capture CO 2 emissions • Use of anthracite-based carbon as a catalyst • Use of processed anthracite in carbon electrodes and carbon black • Use of raw coal refuse for producing activated carbon • Reusable PACs to recycle captured mercury • Use of combustion and gasification chars to capture mercury from coal-fired power plants • Development of a synthetic coal tar enamel • Use of alternative binder pitches in aluminum anodes • Use of Solvent Extracted Carbon Ore (SECO) to fuel a carbon fuel cell • Production of a low cost coal-derived turbostratic carbon powder for structural applications • Production of high-value carbon fibers and foams via the co-processing of a low-cost coal extract pitch with well-dispersed carbon nanotubes • Use of carbon from fly ash as metallurgical carbon • Production of bulk carbon fiber for concrete reinforcement • Characterizing coal solvent extraction processes Although some of the projects funded did not meet their original goals, the overall objectives of the CPCPC were completed as many new applications for coal-derived feedstocks have been researched. Future research in many of these areas is necessary before implementation into industry. Potential Application for Exfoliated Anthracite: Filler in CathodesThe Pennsylvania State University -Subcontract # 2486-TPSU-DOE-0350…………….19 Use of Coal Gasification and Combustion Chars for Mercury CaptureThe Pennsylvania State University -Subcontract # 2482-TPSU-DOE-0350…………….46 Binding Efficiency of Coal-Derived Binders Towards Anode ButtsThe EXECUTIVE SUMMARYThe objective of these projects was to investigate alternative technologies for non-fuel uses of coal. Special emphasis was placed on developing premium carbon products from coal-derived feedstocks. A total of 14 projects, which are the 2003 Research Projects, are reported herein. These projects were categorized into three overall objectives. They are:(1) To explore new applications for the use of anthracite in order to improve its marketability; (2) To effectively minimize environmenta...

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