The eventual leadership in dynamic mobile networking environments

2007-2008 > Academic research: refereed > Refereed conference paperVersion of RecordPublishe

Community Building for Children’s Health: Lessons From Community Partnerships for Healthy Children

· This article describes Community Partnerships for Healthy Children (CPHC), a 10-year, $17 million initiative of the Sierra Health Foundation targeted at improving children’s health in northern California by mobilizing communities to use their assets. Implementation grants were modest ($50,000 annually), but technical assistance and communications support were also provided. · The initiative rolled out in four phases. Overall, a total of 31 communities participated in the initiative. Twenty-six communities remained through phase three, with 18 engaging in the final fourth phase. · Evidence indicates that CPHC improved the health of some children in some communities with regard to some outcomes, but did not improve the health of children at the population level. Community building appears to be well-suited to devising and implementing successful strategies to address straightforward health issues in the short term; more time, resources, and expertise are needed for more complex problems. · The community collaboratives achieved many of the intermediate goals of the initiative. The evidence is strong that communities did identify and respond to needs. · Most of the collaboratives on their own had access to few resources initially, but over time they were able to gather fiscal and human resources from a variety of sources and combine them to provide services such as recreation programs or family resource centers. Collaboratives involved in the final grant stage had been able to raise from other sources an amount nearly twice the foundation’s investment in CPHC. · The collaboratives were similar in role but differed in many other ways, such as the geographic scope and the existing assets. Collaboratives that had members with certain skills (such as grantwriting, public relations, and computer skills) had greater success

Contributions on agreement in dynamic distributed systems

139 p.This Ph.D. thesis studies the agreement problem in dynamic distributed systems by integrating both the classical fault-tolerance perspective and the more recent formalism based on evolving graphs. First, we developed a common framework that allows to analyze and compare models of dynamic distributed systems for eventual leader election. The framework extends a previous proposal by Baldoni et al. by including new dimensions and levels of dynamicity. Also, we extend the Time-Varying Graph (TVG) formalism by introducing the necessary timeliness assumptions and the minimal conditions to solve agreement problems. We provide a hierarchy of time-bounded, TVG-based, connectivity classes with increasingly stronger assumptions and specify an implementation of Terminating Reliable Broadcast for each class. Then we define an Omega failure detector, W, for the eventual leader election in dynamic distributed systems, together with a system model, , which is compatible with the timebounded TVG classes. We implement an algorithm that satisfy the properties of W in M. According to our common framework, M results to be weaker than the previous proposed dynamic distributed system models for eventual leader election. Additionally we use simulations to illustrate this fact and show that our leader election algorithm tolerates more general (i.e., dynamic) behaviors, and hence it is of application in a wider range of practical scenarios at the cost of a moderate overhead on stabilization times

Implementing the weakest failure detector for solving consensus

The concept of unreliable failure detector was introduced by Chandra and Toueg as a mechanism that provides information about process failures. This mechanism has been used to solve several agreement problems, such as the consensus problem. In this paper, algorithms that implement failure detectors in partially synchronous systems are presented. First two simple algorithms of the weakest class to solve the consensus problem, namely the Eventually Strong class (⋄S), are presented. While the first algorithm is wait-free, the second algorithm is f-resilient, where f is a known upper bound on the number of faulty processes. Both algorithms guarantee that, eventually, all the correct processes agree permanently on a common correct process, i.e. they also implement a failure detector of the class Omega (Ω). They are also shown to be optimal in terms of the number of communication links used forever. Additionally, a wait-free algorithm that implements a failure detector of the Eventually Perfect class (⋄P) is presented. This algorithm is shown to be optimal in terms of the number of bidirectional links used forever

Why are IPTp Coverage Targets so Elusive in Sub-Saharan Africa? A Systematic Review of Health System Barriers.

Use of intermittent preventive treatment (IPTp) is a proven cost-effective intervention for preventing malaria in pregnancy. However, despite the roll-out of IPTp policies across Africa more than ten years ago, utilization levels remain low. This review sought to consolidate scattered evidence as to the health system barriers for IPTp coverage in the continent.Methods and findings: Relevant literature from Africa was systematically searched, reviewed and synthesized. Only studies containing primary data were considered. Studies reveal that: (i) poor leadership and governance contribute to slow decentralization of programme management, lack of harmonized guidelines, poor accountability mechanisms, such as robust monitoring and evaluation systems; (ii) low budgetary allocation towards policy implementation slows scale-up, while out-of-pocket expenditure deters women from seeking antenatal services that include IPTp; (iii) there are rampant human resource challenges including low staff motivation levels attributed to such factors as incorrect knowledge of IPTp recommendations and inadequate staffing; (iv) implementation of IPTp policies is hampered by prevailing service delivery barriers, such as long waiting time, long distances to health facilities and poor service provider/client relations; and (v) drug stock-outs and poor management of information and supply chains impair sustained availability of drugs for IPTp. For successful IPTp policy implementation, it is imperative that malaria control programmes target health system barriers that result in low coverage and hence programme ineffectiveness

The Political Economy of Privatization

International organizations promote privatization as precondition for economic development. But is there really too little privatization? This political economy model asks for the incentives of governments to privatize or restructure a state-owned firm. Different government types are compared to identify the political and institutional determinants of privatization. Under privatization, governments commit not to influence the profit-maximizing employment choice by private investors. With respect to the social optimum, both voter-oriented and egoistic governments can have inefficiently high incentives to privatize. When this is the case, outside pressure to privatize is detrimental. An improving institutional environment reduces these inefficiencies

Refining self-propelled particle models for collective behaviour

Swarming, schooling, flocking and herding are all names given to the wide variety of collective behaviours exhibited by groups of animals, bacteria and even individual cells. More generally, the term swarming describes the behaviour of an aggregate of agents (not necessarily biological) of similar size and shape which exhibit some emergent property such as directed migration or group cohesion. In this paper we review various individual-based models of collective behaviour and discuss their merits and drawbacks. We further analyse some one-dimensional models in the context of locust swarming. In specific models, in both one and two dimensions, we demonstrate how varying the parameters relating to how much attention individuals pay to their neighbours can dramatically change the behaviour of the group. We also introduce leader individuals to these models with the ability to guide the swarm to a greater or lesser degree as we vary the parameters of the model. We consider evolutionary scenarios for models with leaders in which individuals are allowed to evolve the degree of influence neighbouring individuals have on their subsequent motion