3,010 research outputs found

    Highly sensitive alkane odour sensors based on functionalised gold nanoparticles

    No full text
    We deposit dense, ordered, thin films of Au-dodecanethiol core/shell nanoparticles by the Langmuir-Schafer (LS) printing method, and find that their resistance at ambient temperature responds selectively and sensitively to alkane odours. Response is a rapid resistance increase due to swelling, and is strongest for alkane odours where the alkane chain is similar in length to the dodecane shell. For decane odours, we find a response to concentrations as low as 15 ppm, about 600 times below the lower explosive limit. Response is weaker, but still significant, to aromatic odours (e.g. Toluene, Xylene), while potential interferants such as polar and/or hydrogen-bonding odours (e.g. alcohols, ketones, water vapour) are somewhat rejected. Resistance is weakly dependent on temperature, and recovers rapidly and completely to its original value within the error margin of measurement. (C) 2011 Elsevier B.V. All rights reserved

    Localization of adaptive variants in human genomes using averaged one-dependence estimation.

    Get PDF
    Statistical methods for identifying adaptive mutations from population genetic data face several obstacles: assessing the significance of genomic outliers, integrating correlated measures of selection into one analytic framework, and distinguishing adaptive variants from hitchhiking neutral variants. Here, we introduce SWIF(r), a probabilistic method that detects selective sweeps by learning the distributions of multiple selection statistics under different evolutionary scenarios and calculating the posterior probability of a sweep at each genomic site. SWIF(r) is trained using simulations from a user-specified demographic model and explicitly models the joint distributions of selection statistics, thereby increasing its power to both identify regions undergoing sweeps and localize adaptive mutations. Using array and exome data from 45 ‡Khomani San hunter-gatherers of southern Africa, we identify an enrichment of adaptive signals in genes associated with metabolism and obesity. SWIF(r) provides a transparent probabilistic framework for localizing beneficial mutations that is extensible to a variety of evolutionary scenarios

    Emergence of the Shackleton Range from beneath the Antarctic Ice Sheet due to glacial erosion

    Get PDF
    This paper explores the long-term evolution of a subglacial fjord landscape in the Shackleton Range, Antarctica. We propose that prolonged ice-sheet erosion across a passive continental margin caused troughs to deepen and lower the surrounding ice-sheet surface, leaving adjacent mountains exposed. Geomorphological evidence suggests a change in the direction of regional ice flow accompanied emergence. Simple calculations suggest that isostatic compensation caused by the deepening of bounding ice-stream troughs lowered the ice-sheet surface relative to the mountains by ~800m. Use of multiple cosmogenic isotopes on bedrock and erratics (26Al, 10Be, 21Ne) provides evidence that overriding of the massif and the deepening of the adjacent troughs occurred earlier than the Quaternary. Perhaps this occurred in the mid-Miocene, as elsewhere in East Antarctica in the McMurdo Dry Valleys and the Lambert basin. The implication is that glacial erosion instigates feedback that can change ice-sheet thickness, extent, and direction of flow. Indeed, as the subglacial troughs evolve over millions of years, they increase topographic relief; and this changes the dynamics of the ice sheet. © 2013 Elsevier B.V

    Memory-Based Snowdrift Game on Networks

    Full text link
    We present a memory-based snowdrift game (MBSG) taking place on networks. We found that, when a lattice is taken to be the underlying structure, the transition of spatial patterns at some critical values of the payoff parameter is observable for both 4 and 8-neighbor lattices. The transition points as well as the styles of spatial patterns can be explained by local stability analysis. In sharp contrast to previously reported results, cooperation is promoted by the spatial structure in the MBSG. Interestingly, we found that the frequency of cooperation of the MBSG on a scale-free network peaks at a specific value of the payoff parameter. This phenomenon indicates that properly encouraging selfish behaviors can optimally enhance the cooperation. The memory effects of individuals are discussed in detail and some non-monotonous phenomena are observed on both lattices and scale-free networks. Our work may shed some new light on the study of evolutionary games over networks.Comment: 6 pages, 6 figures, to be published in Phys. Rev.

    Laser detection utilizing coherence

    Get PDF
    Lasers are an unnatural occurrence, rendered almost impossible in nature due to the laws of thermodynamics. Thus, the presence of laser radiation is always accompanied by an intent for that laser such as sensing, targeting, range finding etc. Detection of laser radiation is therefore important as it may be a precursor to impending action. Laser warning receivers have been around for decades and have been aligned with the type of laser threat. In the last few years new threats have appeared in the form of low-cost diode lasers with dangerously high power levels (several Watts for a few hundred US dollars) and an ever expanding range of wavelengths. Protecting against such threats requires its detection, analysis and classification. In this paper we will discuss the types of technologies that have been used to detect lasers and the properties they can discern. We then focus on the developments in the detection of coherence properties and its ability to detect weak continuous wave (CW) laser sources

    Factors influencing researchers’ journal selection decisions

    Get PDF
    The scholarly publication landscape continues to grow in complexity, presenting researchers with ever-increasing dilemmas regarding journal choice. However, research into the decision-making processes associated with journal choice is limited. This article contributes by reporting on an international survey of researchers in various disciplines and with varying levels of experience. The study examines the extent to which various journal characteristics affect journal selection, perceptions of the extent to which university and national research policies impact on their journal choice, and the influence of academics’ familiarity, confidence and objectives on journal choice. The most important factors influencing journal choice were as follows: reliability of reviewing, usefulness of reviewers’ feedback, the reputation of the journal and confidence that their article is in scope for the journal. Publishing productivity, publishing experience, researcher role and discipline had little impact on the ranking of journal choice factors, suggesting that the research community is homogeneous

    Preference purification and the inner rational agent:A critique of the conventional wisdom of behavioural welfare economics

    Get PDF
    Neoclassical economics assumes that individuals have stable and context-independent preferences, and uses preference-satisfaction as a normative criterion. By calling this assumption into question, behavioural findings cause fundamental problems for normative economics. A common response to these problems is to treat deviations from conventional rational-choice theory as mistakes, and to try to reconstruct the preferences that individuals would have acted on, had they reasoned correctly. We argue that this preference purification approach implicitly uses a dualistic model of the human being, in which an inner rational agent is trapped in an outer psychological shell. This model is psychologically and philosophically problematic

    A dynamically extending exclusion process

    Full text link
    An extension of the totally asymmetric exclusion process, which incorporates a dynamically extending lattice is explored. Although originally inspired as a model for filamentous fungal growth, here the dynamically extending exclusion process (DEEP) is studied in its own right, as a nontrivial addition to the class of nonequilibrium exclusion process models. Here we discuss various mean-field approximation schemes and elucidate the steady state behaviour of the model and its associated phase diagram. Of particular note is that the dynamics of the extending lattice leads to a new region in the phase diagram in which a shock discontinuity in the density travels forward with a velocity that is lower than the velocity of the tip of the lattice. Thus in this region the shock recedes from both boundaries.Comment: 20 pages, 12 figure
    • 

    corecore