66 research outputs found
The "Unfriending" Problem: The Consequences of Homophily in Friendship Retention for Causal Estimates of Social Influence
An increasing number of scholars are using longitudinal social network data
to try to obtain estimates of peer or social influence effects. These data may
provide additional statistical leverage, but they can introduce new inferential
problems. In particular, while the confounding effects of homophily in
friendship formation are widely appreciated, homophily in friendship retention
may also confound causal estimates of social influence in longitudinal network
data. We provide evidence for this claim in a Monte Carlo analysis of the
statistical model used by Christakis, Fowler, and their colleagues in numerous
articles estimating "contagion" effects in social networks. Our results
indicate that homophily in friendship retention induces significant upward bias
and decreased coverage levels in the Christakis and Fowler model if there is
non-negligible friendship attrition over time.Comment: 26 pages, 4 figure
To What Extent Iron-Pnictide New Superconductors Have Been Clarified: A Progress Report
In this review, the authors present a summary of experimental reports on
newly discovered iron-based superconductors as they were known at the end of
2008. At the same time, this paper is intended to be useful for experimenters
to know the current status of these superconductors. The authors introduce
experimental results that reveal basic physical properties in the normal and
superconducting states. The similarities and differences between iron-pnictide
superconductors and other unconventional superconductors are also discussed.Comment: 20 pages, 32 figures. Open selec
Computer-assisted methods for molecular structure elucidation: realizing a spectroscopist's dream
Evidence for unconventional superconductivity in single crystals of the antiferromagnetic heavy-electron compound URu2Si2
Comprehensive molecular, genomic and phenotypic analysis of a major clone of Enterococcus faecalis MLST ST40
The Short-Term Dynamics of Peers and Delinquent Behavior: An Analysis of Bi-weekly Changes Within a High School Student Network
Adolescent Friendships, BMI, and Physical Activity: Untangling Selection and Influence Through Longitudinal Social Network Analysis
Bioecological theory suggests that adolescents’ health is a result of selection and socialization processes occurring between adolescents and their microsettings. This study examines the association between adolescents’ friends and health using a social network model and data from the National Longitudinal Study of Adolescent Health (N = 1,896, mean age = 15.97 years). Results indicated evidence of friend influence on BMI and physical activity. Friendships were more likely among adolescents who engaged in greater physical activity and who were similar to one another in BMI and physical activity. These effects emerged after controlling for alternative friend selection factors, such as endogenous social network processes and propinquity through courses and activities. Some selection effects were moderated by gender, popularity, and reciprocity
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