Comparing community structure identification

We compare recent approaches to community structure identification in terms of sensitivity and computational cost. The recently proposed modularity measure is revisited and the performance of the methods as applied to ad hoc networks with known community structure, is compared. We find that the most accurate methods tend to be more computationally expensive, and that both aspects need to be considered when choosing a method for practical purposes. The work is intended as an introduction as well as a proposal for a standard benchmark test of community detection methods.Comment: 10 pages, 3 figures, 1 table. v2: condensed, updated version as appears in JSTA

Stratospheric aerosol - Observations, processes, and impact on climate

Interest in stratospheric aerosol and its role in climate have increased over the last decade due to the observed increase in stratospheric aerosol since 2000 and the potential for changes in the sulfur cycle induced by climate change. This review provides an overview about the advances in stratospheric aerosol research since the last comprehensive assessment of stratospheric aerosol was published in 2006. A crucial development since 2006 is the substantial improvement in the agreement between in situ and space-based inferences of stratospheric aerosol properties during volcanically quiescent periods. Furthermore, new measurement systems and techniques, both in situ and space based, have been developed for measuring physical aerosol properties with greater accuracy and for characterizing aerosol composition. However, these changes induce challenges to constructing a long-term stratospheric aerosol climatology. Currently, changes in stratospheric aerosol levels less than 20% cannot be confidently quantified. The volcanic signals tend to mask any nonvolcanically driven change, making them difficult to understand. While the role of carbonyl sulfide as a substantial and relatively constant source of stratospheric sulfur has been confirmed by new observations and model simulations, large uncertainties remain with respect to the contribution from anthropogenic sulfur dioxide emissions. New evidence has been provided that stratospheric aerosol can also contain small amounts of nonsulfate matter such as black carbon and organics. Chemistry-climate models have substantially increased in quantity and sophistication. In many models the implementation of stratospheric aerosol processes is coupled to radiation and/or stratospheric chemistry modules to account for relevant feedback processes

Determinants of Collaborative Leadership: Civic Engagement, Gender or Organizational Norms?

This analysis attempts to unravel competing explanations of collaborative leadership styles of state legislative committee chairs. Specifically, the paper considers the influence of community or volunteer experience, gender, and institutional variables. The data show that women chairs are more likely than their male peers to cite as valuable the leadership skills and experiences that they gain through community and volunteer experience. Compared to their male colleagues, women committee chairs on average also report a greater reliance on collaborative strategies in the management of their committees. Prior community or volunteer experience has little or no direct effect on collaborative styles. In contrast, institutional factors have a much stronger and countervailing influence. Legislative professionalization produces a strong negative effect on collaborative style. Results suggest that conformity to institutional norms may be a more compelling influence than prior community experience. The analysis also points to the gendered nature of organizational leadership with men's and women's styles showing different associations to style depending on the number and power of women in a legislature.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline