Secure Transmission with Optimal Power Allocation in Untrusted Relay Networks

We consider the problem of secure transmission in two-hop amplify-and-forward untrusted relay networks. We analyze the ergodic secrecy capacity (ESC) and present compact expressions for the ESC in the high signal-to-noise ratio regime. We also examine the impact of large scale antenna arrays at either the source or the destination. For large antenna arrays at the source, we confirm that the ESC is solely determined by the channel between the relay and the destination. For very large antenna arrays at the destination, we confirm that the ESC is solely determined by the channel between the source and the relay.

Youth in Contexts of Political Violence: A Developmental Approach to the Study of Youth Identity and Emotional Security in Their Communities

Going beyond the association between youth exposure to political violence and psychopathology, the current article examines within-person change in youth strength of identity with their ethno-political group and youth reports of the insecurity in their communities. Conceptually related but growing out of different paradigms, both group identity and emotional insecurity have been examined as key variables impacting youth responses to threats from other group members. The goal of the current study is to review previous studies examining these two key variables and to contribute new analyses, modeling within-person change in both variables and examining covariation in their growth. The current article uses data from 823 Belfast adolescents over 4 years. The results suggest youth are changing linearly over age in both constructs and that there are ethno-political group differences in how youth are changing. The results also indicate that change in insecurity is related to strength of identity at age 18, and strength of identity and emotional insecurity are related at age 18. Implications and directions for future work in the area of youth and political violence are discussed. © 2014 American Psychological Association.

A Social–Ecological, Process-Oriented Perspective on Political Violence and Child Development

Youth's risk for adjustment problems amid political violence is well documented, but outcomes vary widely, with many children functioning well. Accordingly, researchers are seeking to identify the mechanisms and conditions that contribute to children's adjustment, with an interest in understanding effects on children in terms of changes in the social contexts in which they live and the psychological processes engaged by these social ecologies. In this article, we look at the importance of studying many levels of the social ecology and of differentiating the effects of exposure to contexts of political versus nonpolitical violence, and we address theories about explanatory processes. We review research pertinent to these themes, including a six-wave longitudinal study on political violence and children in Northern Ireland.

Transmission Potential of Rift Valley Fever virus over the course of the 2010 epidemic in South Africa

A Rift Valley fever (RVF) epidemic affecting animals on domestic livestock farms was reported in South Africa during January-August 2010. The first cases occurred after heavy rainfall, and the virus subsequently spread countrywide. To determine the possible effect of environmental conditions and vaccination on RVF virus transmissibility, we estimated the effective reproduction number (R) for the virus over the course of the epidemic by extending the Wallinga and Teunis algorithm with spatial information. Re reached its highest value in mid-February and fell below unity around mid-March, when vaccination coverage was 7.5%-45.7% and vector-suitable environmental conditions were maintained. The epidemic fade-out likely resulted first from the immunization of animals following natural infection or vaccination. The decline in vector-suitable environmental conditions from April onwards and further vaccination helped maintain R below unity. Increased availability of vaccine use data would enable evaluation of the effect of RVF vaccination campaigns.