The speed of range shifts in fragmented landscapes

Peer reviewedPublisher PD

Discovering Evolutionary Stepping Stones through Behavior Domination

Behavior domination is proposed as a tool for understanding and harnessing the power of evolutionary systems to discover and exploit useful stepping stones. Novelty search has shown promise in overcoming deception by collecting diverse stepping stones, and several algorithms have been proposed that combine novelty with a more traditional fitness measure to refocus search and help novelty search scale to more complex domains. However, combinations of novelty and fitness do not necessarily preserve the stepping stone discovery that novelty search affords. In several existing methods, competition between solutions can lead to an unintended loss of diversity. Behavior domination defines a class of algorithms that avoid this problem, while inheriting theoretical guarantees from multiobjective optimization. Several existing algorithms are shown to be in this class, and a new algorithm is introduced based on fast non-dominated sorting. Experimental results show that this algorithm outperforms existing approaches in domains that contain useful stepping stones, and its advantage is sustained with scale. The conclusion is that behavior domination can help illuminate the complex dynamics of behavior-driven search, and can thus lead to the design of more scalable and robust algorithms.Comment: To Appear in Proceedings of the Genetic and Evolutionary Computation Conference (GECCO 2017

Non-blind watermarking of network flows

Linking network flows is an important problem in intrusion detection as well as anonymity. Passive traffic analysis can link flows but requires long periods of observation to reduce errors. Active traffic analysis, also known as flow watermarking, allows for better precision and is more scalable. Previous flow watermarks introduce significant delays to the traffic flow as a side effect of using a blind detection scheme; this enables attacks that detect and remove the watermark, while at the same time slowing down legitimate traffic. We propose the first non-blind approach for flow watermarking, called RAINBOW, that improves watermark invisibility by inserting delays hundreds of times smaller than previous blind watermarks, hence reduces the watermark interference on network flows. We derive and analyze the optimum detectors for RAINBOW as well as the passive traffic analysis under different traffic models by using hypothesis testing. Comparing the detection performance of RAINBOW and the passive approach we observe that both RAINBOW and passive traffic analysis perform similarly good in the case of uncorrelated traffic, however, the RAINBOW detector drastically outperforms the optimum passive detector in the case of correlated network flows. This justifies the use of non-blind watermarks over passive traffic analysis even though both approaches have similar scalability constraints. We confirm our analysis by simulating the detectors and testing them against large traces of real network flows

Waiting Longer Before Claiming, and Activating Youth: No Point?

In Belgium school-leavers are entitled to unemployment benefits after a waiting period and eligible to intensified counselling and training in the Youth Work Plan (YWP) if a job is not found within three months. The length of the waiting period and eligibility to the YWP are sharply determined by two distinct age thresholds. These are exploited to estimate the impact of these policies on the transition rate to employment and on the quality of work. Both policies increase job finding only slightly and insignificantly. The accepted wage is unaffected, but the number of working days falls and, hence, also earnings

Combined Structural Interventions for Gender Equality and Livelihood Security: A Critical Review of the Evidence from Southern and Eastern Africa and the Implications for Young People

This document presents information on how young people in southern and eastern Africa remain disproportionately vulnerable to HIV with gender inequalities and livelihood insecurities being key drivers of this. Behavioural HIV prevention interventions have had weak outcomes and a new generation of structural interventions have emerged seeking to challenge the wider drivers of the HIV epidemic, including gender inequalities and livelihood insecurities. We searched key academic data bases to identify interventions that simultaneously sought to strengthen people's livelihoods and transform gender relationships that had been evaluated in southern and eastern Africa. Our initial search identified 468 articles. We manually reviewed these and identified nine interventions that met our criteria for inclusion. We clustered the nine interventions into three groups: microfinance and gender empowerment interventions; supporting greater participation of women and girls in primary and secondary education; and gender empowerment and financial literacy interventions. We summarise the strengths and limitations of these interventions, with a particular focus on what lessons may be learnt for young people

Ethical Challenges of Randomized Violence Intervention Trials: Examining the SHARE intervention in Rakai, Uganda.

ObjectiveWe identify complexities encountered, including unanticipated crossover between trial arms and inadequate 'standard of care' violence services, during a cluster randomized trial (CRT) of a community-level intimate partner violence (IPV) and HIV prevention intervention in Uganda.MethodsConcepts in public health ethics - beneficence, social value of research, fairness, standard of care, and researcher responsibilities for post-trial benefits - are used to critically reflect on lessons learned and guide discussion on practical and ethical challenges of violence intervention CRTs.ResultsExisting ethical guidelines provide incomplete guidance for responding to unexpected crossover in CRTs providing IPV services. We struggled to balance duty of care with upholding trial integrity, and identifying and providing appropriate standard of care. While we ultimately offered short-term IPV services to controls, we faced additional challenges related to sustaining services beyond the 'short-term' and post-trial.ConclusionStudies evaluating community-level violence interventions, including those combined with HIV reduction strategies, are limited yet critical for developing evidence-based approaches for effectively preventing IPV. Although CRTs are a promising design, further guidance is needed to implement trials that avoid introducing tensions between validity of findings, researchers' responsibilities to protect participants, and equitable distribution of CRT benefits