Decentralized Replication Mechanisms in Deno

We are currently finalizing the design of Deno, a new shared-object system intended for use with repli-cated mobile and wide-area data. The broad aim of our research is to develop a framework for highly-available, decentralized shared-object protocols. The key idea is that our protocols will support high availability through a distributed voting scheme. Specifically, we will investigate (a) peer-to-peer up-dates, which will allow incremental progress to be made in the absence of full connectivity between com-ponent servers, (b) voting rather than centralized schemes for committing updates, ensuring that no sin-gle point of failure can prevent updates from being committed, and (c) application-specific consistency control, allowing applications to relax coherency constraints in ways that do not break the application's notion of consistency. Distribution and multiple connectivity modes are becoming the norm rather than the exception in current computing environments. Thus, we expect the impact of our research to be felt in areas as disparate as mobile computing and collaborative data warehousing on the Internet. (Also cross-referenced as UMIACS-TR-98-54

Mammal predation by an ariid catfish in a dryland river of Western Australia

The presence of the spinifex hopping mouse Notomys alexis in the diet of lesser salmon catfish Neoarius graeffei from the Ashburton River, Western Australia, is reported for the first time. The consumption of terrestrial mammals by Australian freshwater fishes is widely considered to be an infrequent occurrence, of limited importance to aquatic food webs. However, remains of N. alexis were present within the stomachs of 44% of N. graeffei sampled, constituting approximately 95% of the total stomach contents. These findings suggest that N. graeffei will consume large quantities of terrestrial vertebrates when available, and may represent a valuable energy source for this ecologically important species in dryland river

Mechanical challenges to freshwater residency in sharks and rays

Major transitions between marine and freshwater habitats are relatively infrequent, primarily as a result of major physiological and ecological challenges. Few species of cartilaginous fish have evolved to occupy freshwater habitats. Current thought suggests that the metabolic physiology of sharks has remained a barrier to the diversification of this taxon in freshwater ecosystems. Here, we demonstrate that the physical properties of water provide an additional constraint for this species-rich group to occupy freshwater systems. Using hydromechanical modeling, we show that occurrence in fresh water results in a two- to three-fold increase in negative buoyancy for sharks and rays. This carries the energetic cost of lift production and results in increased buoyancy-dependent mechanical power requirements for swimming and increased optimal swim speeds. The primary source of buoyancy, the lipidrich liver, offers only limited compensation for increased negative buoyancy as a result of decreasing water density; maintaining the same submerged weight would involve increasing the liver volume by very large amounts: 3- to 4-fold in scenarios where liver density is also reduced to currently observed minimal levels and 8-fold without any changes in liver density. The first data on body density from two species of elasmobranch occurring in freshwater (the bull shark Carcharhinus leucas, Muller and Henle 1839, and the largetooth sawfish Pristis pristis, Linnaeus 1758) support this hypothesis, showing similar liver sizes as marine forms but lower liver densities, but the greatest negative buoyancies of any elasmobranch studied to date. Our data suggest that the mechanical challenges associated with buoyancy control may have hampered the invasion of freshwater habitats in elasmobranchs, highlighting an additional key factor that may govern the predisposition of marine organisms to successfully establish in freshwater habitats

A Security Infrastructure for Mobile Transactional Systems

In this paper, we present an infrastructure for providing secure transactional replication support for peer-to-peer, decentralized databases. We first describe how to effectively provide protection against external threats, malicious actions by servers not authorized to access data, using conventional cryp-tography-based mechanisms. We then classify and present algorithms that provide protection against internal threats, malicious actions by authenticated servers that misrepresent protocol-specific infor-mation. Our approach to handling internal threats uses both cryptographic techniques and modifica-tions to the update commit criteria. The techniques we propose are unique in that they not only enable a tradeoff between performance and the degree of tolerance to malicious servers, but also allow for indi-vidual servers to support non-uniform degrees of tolerance without adversely affecting the performance of the rest of the system. We investigate the cost of our security mechanisms in the context of Deno: a prototype object replica-tion system designed for use in mobile and weakly-connected environments. Experimental results reveal that protecting against internal threats comes at a cost, but the marginal cost for protecting against larger cliques of malicious insiders is generally low. Furthermore, comparison with a decentralized Read-One Write-All protocol shows that our approach performs significantly better under various workloads. (Also cross-referenced as UMIACS-TR-2000-59

Matching Jobs to Resources in Distributed Desktop Grid Environments

Desktop grids use opportunistic sharing to exploit large collections of personal computers and workstations across the Internet and can achieve tremendous computing power with low cost. However, current systems are typically based on a traditional client-server architecture, which has inherent shortcomings with respect to robustness, reliability and scalability. In this paper, we propose a decentralized, robust, highly available, and scalable infrastructure to match incoming jobs to available resources. The key idea behind our proposed system is to leverage information provided by an underlying peer-to-peer system to create a hierarchical Rendezvous Node Tree, which performs the matching efficiently. Our experimental results obtained via simulation show that we can effectively match jobs with varying levels of resource constraints to available nodes and maintain good load balance in a fully decentralized heterogeneous computational environment

Visceral learning as concept identification

Abstract only. Permission to include in repository granted by Sally Byers, Permissions Assistant, Wiley-Blackwell Publishing Ltd.Visceral learning may be depicted as a process in which subjects seek information about the behavioral goal. Concepts of this goal are based initially upon procedural details of training and are modified as feedback identifies instances of the target response. This approach was assessed by determining whether subjects were capable of describing activities associated with the visceral target after feedback training. Two groups were given visual feedback for changes in heart rate (HR) or lateralized skin conductance (LSC). The two visceral targets within each group (HR: inc/dec; LSC: L>R/R>L) were designated as Response A and Response B. Production of the response on A and B trials in the presence (Training) and absence (Transfer) of feedback was measured. After a one-hour session subjects were asked, without prior notification, to provide written reports describing what they did to control feedback on A and B trials. Awareness of the response was assessed by determining whether judges given the reports successfully identified the visceral target which was required on A and B trials for each subject. Awareness of activities related to feedback was also assessed by quantitative scales completed by the subjects after the written report. Awareness of the response was demonstrated on identification tasks for each experimental condition (HR and LSC). Furthermore, awareness (measured as probability ofcorrect identification) was significantly correlated with performance during Training and Transfer in the HR oroup, but this relationship was obtained only for Transfer in the LSC condition. Transfer without awareness was not observed in either group. Scale ratings did not differ between the visceral targets in either training condition. However, awareness was confirmed by significant correlations between these ratings and visceral performance for Training and Transfer in the HR group and for Transfer in the LSC group. These findings suggest that veridical concepts of the behavioral goal are formed during visceral learning. The concept-formation process appears important to Transfer but does not fully explain performance on feedback trials in the LSC experiment. (Supported by A0132 from NSERC of Canada)Ye

Measuring the Effectiveness of Photoresponsive Nanocomposite Coatings on Aircraft Windshields to Mitigate Laser Intensity

In 2004, pilots reported 46 laser illumination events to the Federal Aviation Administration (FAA), with the number increasing to approximately 3,600 in 2011. Since that time, the number of reported laser incidents has ranged from 3,500 to 4,000. Previous studies indicate the potential for flight crewmember distraction from bright laser light being introduced to the cockpit. Compositional variations of the photoresponsive nanocomposite coatings were applied to an aircraft windscreen using a modified liquid dispersion/heating curing process. The attenuating effects of the deposited films on laser light intensity were evaluated using an optical power meter and the resultant laser intensity data through treated and untreated windscreens was collected. Data revealed a reduction in laser intensity (36–88%) in the presence of the engineered photoresponsive nanocomposite films. Results lend support of the view that the addition of transparent laser attenuating films applied to aircraft windscreens may improve flight safety, and reduce the risk from distraction or disruption of flight crewmembers’ vision

Practice nursing in Australia: A review of education and career pathways

<p>Abstract</p> <p>Background</p> <p>Nurses in Australia are often not educated in their pre registration years to meet the needs of primary care. Careers in primary care may not be as attractive to nursing graduates as high-tech settings such as intensive or acute care. Yet, it is in primary care that increasingly complex health problems are managed. The Australian government has invested in incentives for general practices to employ practice nurses. However, no policy framework has been developed for practice nursing to support career development and post-registration education and training programs are developed in an ad hoc manner and are not underpinned by core professional competencies. This paper reports on a systematic review undertaken to establish the available evidence on education models and career pathways with a view to enhancing recruitment and retention of practice nurses in primary care in Australia.</p> <p>Methods</p> <p>Search terms describing education models, career pathways and policy associated with primary care (practice) nursing were established. These search terms were used to search electronic databases. The search strategy identified 1394 citations of which 408 addressed one or more of the key search terms on policy, education and career pathways. Grey literature from the UK and New Zealand internet sites were sourced and examined. The UK and New Zealand Internet sites were selected because they have well established and advanced developments in education and career pathways for practice nurses.</p> <p>Two reviewers examined titles, abstracts and studies, based on inclusion and exclusion criteria. Disagreement between the reviewers was resolved by consensus or by a third reviewer.</p> <p>Results</p> <p>Significant advances have been made in New Zealand and the UK towards strengthening frameworks for primary care nursing education and career pathways. However, in Australia there is no policy at national level prepare nurses to work in primary care sector and no framework for education or career pathways for nurses working in that sector.</p> <p>Conclusion</p> <p>There is a need for national training standards and a process of accreditation for practice nursing in Australia to support the development of a responsive and sustainable nursing workforce in primary care and to provide quality education and career pathways.</p