Random graphs with clustering

We offer a solution to a long-standing problem in the physics of networks, the creation of a plausible, solvable model of a network that displays clustering or transitivity -- the propensity for two neighbors of a network node also to be neighbors of one another. We show how standard random graph models can be generalized to incorporate clustering and give exact solutions for various properties of the resulting networks, including sizes of network components, size of the giant component if there is one, position of the phase transition at which the giant component forms, and position of the phase transition for percolation on the network.Comment: 5 pages, 2 figure

Computer programs for estimating civil aircraft economics

Computer programs for calculating airline direct operating cost, indirect operating cost, and return on investment were developed to provide a means for determining commercial aircraft life cycle cost and economic performance. A representative wide body subsonic jet aircraft was evaluated to illustrate use of the programs

Developing a learning-centred framework for feedback literacy

There is an increasing focus on notions of feedback in which students are positioned as active players rather than recipients of information. These discussions have been either conceptual in character or have an empirical focus on designs to support learners in feedback processes. There has been little emphasis on learners’ perspectives on, and experiences of, the role they play in such processes and what they need in order to benefit from feedback. This study therefore seeks to identify the characteristics of feedback literacy – that is, how students understand and can utilise feedback for their own learning – by analysing students’ views of feedback processes drawing on a substantial data set derived from a study of feedback in two large universities. The analysis revealed seven groupings of learner feedback literacy, including understanding feedback purposes and roles, seeking information, making judgements about work quality, working with emotions, and processing and using information for the benefit of their future work (31 categories in total). By identifying these realised components of feedback literacy, in the form of illustrative examples, the emergent set of competencies can enable investigations of the development of feedback literacy and improve feedback designs in courses through alignment to these standards

Feedback Models for Learning, Teaching and Performance

© Springer Science+Business Media New York 2014. All rights reserved. This chapter focuses on the role of feedback in learning with particular emphasis on its effect on learner performance, motivation and self-regulation. The authors provide a critical account of definitions and models of feedback, tease out the conceptual roots of practice guidelines and highlight how individual, relational and environmental factors can impact on the utility of feedback as a performance changing device. Many of the conceptual models published in the literature draw on theoretical principles rather than empirical data to support the impact of feedback on learning/performance change. The empirical data from a diverse range of disciplines converge to a commonfinding-that written and verbal feedback in practice deviates considerably from principles of effective practice. The reasons for this theory-practice disjunction are explored, and the authors suggest that the lack of adoption of advocated principles may represent a need to look at feedback in a different way. A constructivist view on feedback encourages learners and educators to view feedback as a system of learning, rather than discreet episodes of educators "telling" learners about their performance. Highlighting the need for a shift in conceptual framework is not enough however. What is limited in the feedback literature is how to achieve feedback encounters that are typi fied by learner engagement. We argue that contesting the traditional, behaviourist "feedback ritual" requires leadership from educators, and a deliberate commitment to curricular redesign with purposeful and structured opportunities for learners to engage in feedback episodes, to put into place changes triggered by feedback and finally to re-evaluate performance in relation to set goals. Such a "system-orientated" take on feedback design requires upskilling of both educators and learners and needs to factor in the in fl uence of context, culture and relationships in learning

Oocyte cryopreservation as an adjunct to the assisted reproductive technologies

The document attached has been archived with permission from the editor of the Medical Journal of Australia. An external link to the publisher’s copy is included. See page 2 of PDF for this item.Keith L Harrison, Michelle T Lane, Jeremy C Osborn, Christine A Kirby, Regan Jeffrey, John H Esler and David Mollo

Threshold effects for two pathogens spreading on a network

Diseases spread through host populations over the networks of contacts between individuals, and a number of results about this process have been derived in recent years by exploiting connections between epidemic processes and bond percolation on networks. Here we investigate the case of two pathogens in a single population, which has been the subject of recent interest among epidemiologists. We demonstrate that two pathogens competing for the same hosts can both spread through a population only for intermediate values of the bond occupation probability that lie above the classic epidemic threshold and below a second higher value, which we call the coexistence threshold, corresponding to a distinct topological phase transition in networked systems.Comment: 5 pages, 2 figure

Saturation Mutagenesis of Lysine 12 Leads to the Identification of Derivatives of Nisin A with Enhanced Antimicrobial Activity

peer-reviewedIt is becoming increasingly apparent that innovations from the “golden age” of antibiotics are becoming ineffective, resulting in a pressing need for novel therapeutics. The bacteriocin family of antimicrobial peptides has attracted much attention in recent years as a source of potential alternatives. The most intensively studied bacteriocin is nisin, a broad spectrum lantibiotic that inhibits Gram-positive bacteria including important food pathogens and clinically relevant antibiotic resistant bacteria. Nisin is gene-encoded and, as such, is amenable to peptide bioengineering, facilitating the generation of novel derivatives that can be screened for desirable properties. It was to this end that we used a site-saturation mutagenesis approach to create a bank of producers of nisin A derivatives that differ with respect to the identity of residue 12 (normally lysine; K12). A number of these producers exhibited enhanced bioactivity and the nisin A K12A producer was deemed of greatest interest. Subsequent investigations with the purified antimicrobial highlighted the enhanced specific activity of this modified nisin against representative target strains from the genera Streptococcus, Bacillus, Lactococcus, Enterococcus and Staphylococcus.This work was supported by the Irish Government under the National Development Plan; by the Irish Research Council for Science Engineering and Technology (IRCSET); by Enterprise Ireland; and by Science Foundation Ireland (SFI), through the Alimentary Pharmabiotic Centre (APC) at University College Cork, Ireland, which is supported by the SFI-funded Centre for Science, Engineering and Technology (SFI-CSET) and provided P.D.C., C.H. and R.P.R. with SFI Principal Investigator funding

Self-avoiding walks on scale-free networks

Several kinds of walks on complex networks are currently used to analyze search and navigation in different systems. Many analytical and computational results are known for random walks on such networks. Self-avoiding walks (SAWs) are expected to be more suitable than unrestricted random walks to explore various kinds of real-life networks. Here we study long-range properties of random SAWs on scale-free networks, characterized by a degree distribution $P(k) \sim k^{-\gamma}$. In the limit of large networks (system size $N \to \infty$), the average number $s_n$ of SAWs starting from a generic site increases as $\mu^n$, with $\mu = / - 1$. For finite $N$, $s_n$ is reduced due to the presence of loops in the network, which causes the emergence of attrition of the paths. For kinetic growth walks, the average maximum length, $$, increases as a power of the system size: $\sim N^{\alpha}$, with an exponent $\alpha$ increasing as the parameter $\gamma$ is raised. We discuss the dependence of $\alpha$ on the minimum allowed degree in the network. A similar power-law dependence is found for the mean self-intersection length of non-reversal random walks. Simulation results support our approximate analytical calculations.Comment: 9 pages, 7 figure