1,079 research outputs found
Containing epidemic outbreaks by message-passing techniques
The problem of targeted network immunization can be defined as the one of
finding a subset of nodes in a network to immunize or vaccinate in order to
minimize a tradeoff between the cost of vaccination and the final (stationary)
expected infection under a given epidemic model. Although computing the
expected infection is a hard computational problem, simple and efficient
mean-field approximations have been put forward in the literature in recent
years. The optimization problem can be recast into a constrained one in which
the constraints enforce local mean-field equations describing the average
stationary state of the epidemic process. For a wide class of epidemic models,
including the susceptible-infected-removed and the
susceptible-infected-susceptible models, we define a message-passing approach
to network immunization that allows us to study the statistical properties of
epidemic outbreaks in the presence of immunized nodes as well as to find
(nearly) optimal immunization sets for a given choice of parameters and costs.
The algorithm scales linearly with the size of the graph and it can be made
efficient even on large networks. We compare its performance with topologically
based heuristics, greedy methods, and simulated annealing
Containing Epidemic Outbreaks by Message-Passing Techniques
The problem of targeted network immunization can be defined as the one of finding a subset of nodes in a network to immunize or vaccinate in order to minimize a tradeoff between the cost of vaccination and the final (stationary) expected infection under a given epidemic model. Although computing the expected infection is a hard computational problem, simple and efficient mean-field approximations have been put forward in the literature in recent years. The optimization problem can be recast into a constrained one in which the constraints enforce local mean-field equations describing the average stationary state of the epidemic process. For a wide class of epidemic models, including the susceptible-infected-removed and the susceptible-infected-susceptible models, we define a message-passing approach to network immunization that allows us to study the statistical properties of epidemic outbreaks in the presence of immunized nodes as well as to find (nearly) optimal immunization sets for a given choice of parameters and costs. The algorithm scales linearly with the size of the graph, and it can be made efficient even on large networks. We compare its performance with topologically based heuristics, greedy methods, and simulated annealing on both random graphs and real-world networks
Flight of the dragonflies and damselflies
This work is a synthesis of our current understanding of the mechanics, aerodynamics and visually mediated control of dragonfly and damselfly flight, with the addition of new experimental and computational data in several key areas. These are: the diversity of dragonfly wing morphologies, the aerodynamics of gliding flight, force generation in flapping flight, aerodynamic efficiency, comparative flight performance and pursuit strategies during predatory and territorial flights. New data are set in context by brief reviews covering anatomy at several scales, insect aerodynamics, neuromechanics and behaviour. We achieve a new perspective by means of a diverse range of techniques, including laser-line mapping of wing topographies, computational fluid dynamics simulations of finely detailed wing geometries, quantitative imaging using particle image velocimetry of on-wing and wake flow patterns, classical aerodynamic theory, photography in the field, infrared motion capture and multi-camera optical tracking of free flight trajectories in laboratory environments. Our comprehensive approach enables a novel synthesis of datasets and subfields that integrates many aspects of flight from the neurobiology of the compound eye, through the aeromechanical interface with the surrounding fluid, to flight performance under cruising and higher-energy behavioural modes
Solving the apparent diversity-accuracy dilemma of recommender systems
Recommender systems use data on past user preferences to predict possible
future likes and interests. A key challenge is that while the most useful
individual recommendations are to be found among diverse niche objects, the
most reliably accurate results are obtained by methods that recommend objects
based on user or object similarity. In this paper we introduce a new algorithm
specifically to address the challenge of diversity and show how it can be used
to resolve this apparent dilemma when combined in an elegant hybrid with an
accuracy-focused algorithm. By tuning the hybrid appropriately we are able to
obtain, without relying on any semantic or context-specific information,
simultaneous gains in both accuracy and diversity of recommendations.Comment: 10 pages, 9 figures, 4 tables (final version with supporting
information included
The effect of discrete vs. continuous-valued ratings on reputation and ranking systems
When users rate objects, a sophisticated algorithm that takes into account
ability or reputation may produce a fairer or more accurate aggregation of
ratings than the straightforward arithmetic average. Recently a number of
authors have proposed different co-determination algorithms where estimates of
user and object reputation are refined iteratively together, permitting
accurate measures of both to be derived directly from the rating data. However,
simulations demonstrating these methods' efficacy assumed a continuum of rating
values, consistent with typical physical modelling practice, whereas in most
actual rating systems only a limited range of discrete values (such as a 5-star
system) is employed. We perform a comparative test of several co-determination
algorithms with different scales of discrete ratings and show that this
seemingly minor modification in fact has a significant impact on algorithms'
performance. Paradoxically, where rating resolution is low, increased noise in
users' ratings may even improve the overall performance of the system.Comment: 6 pages, 2 figure
Negotiating queer and religious identities in higher education: queering âprogressionâ in the âuniversity experienceâ
This article addresses the negotiation of âqueer religiousâ student identities in UK higher education. The âuniversity experienceâ has generally been characterised as a period of intense transformation and self-exploration, with complex and overlapping personal and social influences significantly shaping educational spaces, subjects and subjectivities. Engaging with ideas about progressive tolerance and becoming, often contrasted against âbackwardsâ religious homophobia as a sentiment/space/subject âoutsideâ education, this article follows the experiences and expectations of queer Christian students. In asking whether notions of âqueering higher educationâ (Rumens 2014 Rumens, N. 2014. âQueer Business: Towards Queering the Purpose of the Business School.â In The Entrepreneurial University: Public Engagements, Intersecting Impacts, edited by Y. Taylor, 82â104. Basingstoke: Palgrave Macmillan.) âfitâ with queer-identifying religious youth, the article explores how educational experiences are narrated and made sense of as âprogressiveâ. Educational transitions allow (some) sexual-religious subjects to negotiate identities more freely, albeit with ongoing constraints. Yet perceptions of what, where and who is deemed âprogressiveâ and âbackwardsâ with regard to sexuality and religion need to be met with caution, where the âuniversity experienceâ can shape and shake sexual-religious identity
Diagnosis of lethal or prenatal-onset autosomal recessive disorders by parental exome sequencing.
OBJECTIVE: Rare genetic disorders resulting in prenatal or neonatal death are genetically heterogeneous, but testing is often limited by the availability of fetal DNA, leaving couples without a potential prenatal test for future pregnancies. We describe our novel strategy of exome sequencing parental DNA samples to diagnose recessive monogenic disorders in an audit of the first 50 couples referred. METHOD: Exome sequencing was carried out in a consecutive series of 50 couples who had 1 or more pregnancies affected with a lethal or prenatal-onset disorder. In all cases, there was insufficient DNA for exome sequencing of the affected fetus. Heterozygous rare variants (MAF < 0.001) in the same gene in both parents were selected for analysis. Likely, disease-causing variants were tested in fetal DNA to confirm co-segregation. RESULTS: Parental exome analysis identified heterozygous pathogenic (or likely pathogenic) variants in 24 different genes in 26/50 couples (52%). Where 2 or more fetuses were affected, a genetic diagnosis was obtained in 18/29 cases (62%). In most cases, the clinical features were typical of the disorder, but in others, they result from a hypomorphic variant or represent the most severe form of a variable phenotypic spectrum. CONCLUSION: We conclude that exome sequencing of parental samples is a powerful strategy with high clinical utility for the genetic diagnosis of lethal or prenatal-onset recessive disorders. © 2017 The Authors Prenatal Diagnosis published by John Wiley & Sons Ltd
Irreversible inhibitors of the EGF receptor may circumvent acquired resistance to gefitinib
Non-small cell lung cancers (NSCLCs) with activating mutations in the kinase domain of the epidermal growth factor receptor (EGFR) demonstrate dramatic, but transient, responses to the reversible tyrosine kinase inhibitors gefitinib (Iressa) and erlotinib (Tarceva). Some recurrent tumors have a common secondary mutation in the EGFR kinase domain, T790M, conferring drug resistance, but in other cases the mechanism underlying acquired resistance is unknown. In studying multiple sites of recurrent NSCLCs, we detected T790M in only a small percentage of tumor cells. To identify additional mechanisms of acquired resistance to gefitinib, we used NSCLC cells harboring an activating EGFR mutation to generate multiple resistant clones in vitro. These drug-resistant cells demonstrate continued dependence on EGFR and ERBB2 signaling for their viability and have not acquired secondary EGFR mutations. However, they display increased internalization of ligand-activated EGFR, consistent with altered receptor trafficking. Although gefitinib-resistant clones are cross-resistant to related anilinoquinazolines, they demonstrate sensitivity to a class of irreversible inhibitors of EGFR. These inhibitors also show effective inhibition of signaling by T790M-mutant EGFR and killing of NSCLC cells with the T790M mutation. Both mechanisms of gefitinib resistance are therefore circumvented by irreversible tyrosine kinase inhibitors. Our findings suggest that one of these, HKI-272, may prove highly effective in the treatment of EGFR-mutant NSCLCs, including tumors that have become resistant to gefitinib or erlotinib
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