The structure and vulnerability of a drug trafficking collaboration network

Prior research has established that collaboration networks exhibit heavy-tailed degree distributions, assortative degree mixing, and large clustering coefficients. Using court record data, we assess these properties in a collaboration network among heroin traffickers. Consistent with prior research, we find an exponential degree distribution and strong local clustering. However, the traffickers mix dissortatively by degree rather than assortatively. Using a graph sampling method, we show that a consequence of dissortative mixing is that targeted vertex removals have a greater impact on the connectivity and cohesion of the trafficking network. We also note the importance of degree mixing for characterizing and identifying topological weaknesses.     

Back propagation neural networks and multiple regressions in the case of heteroskedasticity

This paper compares the performance between regression analysis and a clustering based neural network approach when the data deviates from the homoscedasticity assumption of regression. Heteroskedasticity is a problem that arises in linear regression due to the unequal error variances. One of the methods to deal heteroskedasticity in classical regression theory is weighted least-square regression (WLS). In order to deal the problem of heteroskedasticity, backpropagation neural network is applied. In this context, an algorithm is proposed which is based on robust estimates of location and dispersion matrix that helps in preserving the error assumption of the linear regression. Analysis is carried out with appropriate designs using simulated data and the results are presented.     

Beyond interviewer effects in the standardized measurement of ego-centric networks

The effects which interviewers exert on the collection of ego-centric networks have recently come into the focus of methodological considerations. Studies consistently show that the size of networks varies depending on the interviewer. We would like to expand on this research strand by pointing to different aspects which have so far gone unremarked in the discussion. First, size is mainly analysed as a network measure which is influenced during data collection, while other common measures such as network density or composition have not received sufficient consideration. Second, large-scale surveys using face-to-face interviews usually allocate interviewers to a single sampling point. Differences between sampling points (locality effects) are attributed to interviewer effects. Hence, we disentangle the effects of the locality and interviewer. Third, the discussion on interviewer effects often follows an “actor-oriented” consideration of how data collection situations are structured by interviewers. Expanding this approach from a relational perspective, we consider the relationship between the interviewers and respondents and whether this relationship influences the collection of network data. To test our hypotheses about the influence of interviewers, the locality and the interviewer-respondent relationship on different network measures, we use data from the 2010 German General Social Survey (n = 2827 respondents, n = 220 interviewers). The multilevel analyses show that the relationship between the interviewer and the respondent is not very relevant. Furthermore, the analyses show that interviewers have an influence on the network size but not on measures of their composition. However, evidence on the prevalence of locality or interviewer effects is mixed. Finally, homophilous interviewer-respondent relationships have very little effect on network characteristics. We find evidence of training and fatigue effects on network size. However, much of the variation in network size caused by the interviewer still remains unexplained. We draw conclusions on how to organize interview situations in surveys.     

Network domains in social networking sites: expectations,meanings, and social capital

This paper examines why the use of social networking sites (SNSs) leads to different results in cultivating bridging and bonding social capital for different groups of people. Based on in-depth interviews of 45 university students in Hong Kong, I find that Mainland Chinese students studying in Hong Kong actively use SNSs for seeking practical information about offline matters, and they obtain substantial enacted support from other Mainland students of the same university through SNS use. As a result, they accumulate both bridging and bonding social capital. Local Hong Kong students, however, use SNSs mainly for social information seeking and are only able to accrue limited bridging social capital through SNS use. Drawing on the theory of network domains, I argue that the different offline network structures in which students are located – namely, homogeneous and closed networks versus heterogeneous and open networks – explain this difference. Students with closed offline networks have defined expectations of online ties; they think of their online activities as practical and leading to real changes in their status among peers. Those with open networks have indefinite expectations of their online audience; thus, they interpret online activities differently, thinking of them as recreational, and they are playful in their online behaviour. These different outcomes of online activities consequently lead to diverse results in social capital accrual.     

A Study of a Network Meeting: Exploring the Interplay between Inner and Outer Dialogues in Significant and Meaningful Moments

The present study is part of a series of qualitative studies focusing on dialogic practice in southern Norway. In this article, we present a qualitative study of a network meeting focusing on the interplay between the participants' inner and outer dialogues. The network meeting is between an adolescent boy, his mother and two network therapists, the same adolescent case discussed previously in this journal by Bøe et al. ( 2013 ). The aim of this study is to explore how the interplay between inner and outer dialogues contributes to significant and meaningful moments for the interlocutors. A multiperspective methodology is used that combines video recordings of a network meeting and participant interviews with text analysis. Our research found the interplay has an important role in understanding the emergence of significant and meaningful moments in therapy. A one‐sided focus on participants' utterances or inner dialogues was insufficient to explain their significance and meaning to the interlocutors. A dialogical approach provides a theoretical frame and concepts that are useful in investigations of therapeutic conversations.     

Ethnic ingroup friendships in schools: Testing the by-product hypothesis in England,Germany, the Netherlands and Sweden

This study set out to examine to what extent ethnic ingroup friendship in secondary school classes are a by-product of cultural and socioeconomic ingroup friendship. Based on homophily theory, we expected similar opinions, leisure activities, religion, risk behaviour and socioeconomic factors to (partly) explain ethnic ingroup preferences. Multilevel p₂ models on 13,272 pupils in 625 secondary school classes in England, Germany, the Netherlands and Sweden showed that adolescents tend to have friends similar in ethnicity, cultural and socioeconomic characteristics. We find no evidence, however, that ethnic homophily is explained by cultural and socioeconomic homophily.