2,274 research outputs found

    Cuttlefish responses to visual orientation of substrates, water flow and a model of motion camouflage

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    Low-level mechanisms in vertebrate vision are sensitive to line orientation. Here we investigate orientation sensitivity in the cuttlefish Sepia pharaonis, by allowing animals to settle on stripe patterns. When camouflaging themselves cuttlefish are known to be sensitive to image parameters such as contrast and spatial scale, but we find no effect of background orientation on the patterns displayed. It is nonetheless clear that the animals see orientation, because they prefer to rest with the body-axis perpendicular to the stripes. We consider three possible mechanisms to account for this behaviour. Firstly, that the body patterns are themselves oriented, and that the cuttlefish align themselves to aid static camouflage. This is unlikely, as the patterns displayed have no dominant orientation at any spatial scale. A second possibility is that motion camouflage favours alignment of the body orthogonal to background stripes, and we suggest how this alignment can minimise motion signals produced by occlusion. Thirdly we show that cuttlefish prefer to rest with their body-axis parallel to the water flow, and it is possible that they use visual patterns such as sand ripples to determine water flow

    Modelling expected physical impacts and human casualties from explosive volcanic eruptions

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    A multi-hazard, multi-vulnerability impact model has been developed for application to European volcanoes that could significantly damage human settlements. This impact model is based on volcanological analyses of the potential hazards and hazard intensities coupled with engineering analyses of the vulnerability to these hazards of residential buildings in four European locations threatened by explosive volcanic eruptions. For a given case study site, inputs to the model are population data, building characteristics, volcano scenarios as a series of hazard intensities, and scenarios such as the time of eruption or the percentage of the population which has been evacuated. Outputs are the rates of fatalities, seriously injured casualties, and destroyed buildings for a given scenario. These results are displayed in a GIS, thereby presenting risk maps which are easy to use for presenting to public officials, the media, and the public. Technical limitations of the model are discussed and future planned developments are considered. This work contributes to the EU-funded project EXPLORIS (Explosive Eruption Risk and Decision Support for EU Populations Threatened by Volcanoes, EVR1-2001-00047). </p><p style='line-height: 20px;'>&nbsp;</p

    Sparse and Constrained Stochastic Predictive Control for Networked Systems

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    This article presents a novel class of control policies for networked control of Lyapunov-stable linear systems with bounded inputs. The control channel is assumed to have i.i.d. Bernoulli packet dropouts and the system is assumed to be affected by additive stochastic noise. Our proposed class of policies is affine in the past dropouts and saturated values of the past disturbances. We further consider a regularization term in a quadratic performance index to promote sparsity in control. We demonstrate how to augment the underlying optimization problem with a constant negative drift constraint to ensure mean-square boundedness of the closed-loop states, yielding a convex quadratic program to be solved periodically online. The states of the closed-loop plant under the receding horizon implementation of the proposed class of policies are mean square bounded for any positive bound on the control and any non-zero probability of successful transmission

    Precautionary Regulation in Europe and the United States: A Quantitative Comparison

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    Much attention has been addressed to the question of whether Europe or the United States adopts a more precautionary stance to the regulation of potential environmental, health, and safety risks. Some commentators suggest that Europe is more risk-averse and precautionary, whereas the US is seen as more risk-taking and optimistic about the prospects for new technology. Others suggest that the US is more precautionary because its regulatory process is more legalistic and adversarial, while Europe is more lax and corporatist in its regulations. The flip-flop hypothesis claims that the US was more precautionary than Europe in the 1970s and early 1980s, and that Europe has become more precautionary since then. We examine the levels and trends in regulation of environmental, health, and safety risks since 1970. Unlike previous research, which has studied only a small set of prominent cases selected non-randomly, we develop a comprehensive list of almost 3,000 risks and code the relative stringency of regulation in Europe and the US for each of 100 risks randomly selected from that list for each year from 1970 through 2004. Our results suggest that: (a) averaging over risks, there is no significant difference in relative precaution over the period, (b) weakly consistent with the flip-flop hypothesis, there is some evidence of a modest shift toward greater relative precaution of European regulation since about 1990, although (c) there is a diversity of trends across risks, of which the most common is no change in relative precaution (including cases where Europe and the US are equally precautionary and where Europe or the US has been consistently more precautionary). The overall finding is of a mixed and diverse pattern of relative transatlantic precaution over the period

    A review of anabolic therapies for osteoporosis

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    Osteoporosis results from a loss of bone mass and bone structure such that the bone becomes weak and fractures with very little trauma. Until recently, the approved osteoporosis therapies prevented more bone loss by altering osteoclast activity and lifespan. Recently, attention has turned away from osteoclast inhibition to agents that can stimulate the osteoblast to form new bone, or anabolic agents. This article reviews both approved and experimental anabolic agents that improve bone mass by improving osteoblast activity, or increasing osteoblast number. The use of the anabolic agents to improve bone mass and strength followed by agents that prevent the new bone mass from being lost may offer the ability to cure osteoporosis and reduce bone fracture healing time

    Exact Bayesian curve fitting and signal segmentation.

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    We consider regression models where the underlying functional relationship between the response and the explanatory variable is modeled as independent linear regressions on disjoint segments. We present an algorithm for perfect simulation from the posterior distribution of such a model, even allowing for an unknown number of segments and an unknown model order for the linear regressions within each segment. The algorithm is simple, can scale well to large data sets, and avoids the problem of diagnosing convergence that is present with Monte Carlo Markov Chain (MCMC) approaches to this problem. We demonstrate our algorithm on standard denoising problems, on a piecewise constant AR model, and on a speech segmentation problem

    Quality and complexity measures for data linkage and deduplication

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    Summary. Deduplicating one data set or linking several data sets are increasingly important tasks in the data preparation steps of many data mining projects. The aim of such linkages is to match all records relating to the same entity. Research interest in this area has increased in recent years, with techniques originating from statistics, machine learning, information retrieval, and database research being combined and applied to improve the linkage quality, as well as to increase performance and efficiency when linking or deduplicating very large data sets. Different measures have been used to characterise the quality and complexity of data linkage algorithms, and several new metrics have been proposed. An overview of the issues involved in measuring data linkage and deduplication quality and complexity is presented in this chapter. It is shown that measures in the space of record pair comparisons can produce deceptive quality results. Various measures are discussed and recommendations are given on how to assess data linkage and deduplication quality and complexity. Key words: data or record linkage, data integration and matching, deduplication, data mining pre-processing, quality and complexity measures

    Toward resourcefulness: pathways for community positive health

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    Communities are powerful and necessary agents for defining and pursuing their health, but outside organizations often adopt community health promotion approaches that are patronizing and top-down. Conversely, bottom-up approaches that build on and mobilize community health assets are often critiqued for tasking the most vulnerable and marginalized communities to use their own limited resources without real opportunities for change. Taking into consideration these community health promotion shortcomings, this article asks how communities may be most effectively and appropriately supported in pursuing their health. This article reviews how community health is understood, moving from negative to positive conceptualizations; how it is determined, moving from a risk-factor orientation to social determination; and how it is promoted, moving from top-down to bottom-up approaches. Building on these understandings, we offer the concept of ‘resourcefulness’ as an approach to strengthen positive health for communities, and we discuss how it engages with three interrelated tensions in community health promotion: resources and sustainability, interdependence and autonomy, and community diversity and inclusion. We make practical suggestions for outside organizations to apply resourcefulness as a process-based, place-based, and relational approach to community health promotion, arguing that resourcefulness can forge new pathways to sustainable and self-sustaining community positive health

    Puppeteering as a metaphor for unpacking power in participatory action research on climate change and health

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    The health impacts of climate change are distributed inequitably, with marginalized communities typically facing the direst consequences. However, the concerns of the marginalized remain comparatively invisible in research, policy and practice. Participatory action research (PAR) has the potential to centre these concerns, but due to unequal power relations among research participants, the approaches often fall short of their emancipatory ideals. To unpack how power influences the dynamics of representation in PAR, this paper presents an analytical framework using the metaphor of ‘puppeteering’. Puppeteering is a metaphor for how a researcher-activist resonates and catalyses both the voices (ventriloquism) and actions (marionetting) of a marginalized community. Two questions and continuums are central to the framework. First, who and where the puppeteer is (insider and outsider agents). Second, what puppeteering is (action and research; radical and managerial). Examples from climate change and health research provide illustrations and contextualizations throughout. A key complication for applying PAR to address the health impacts of climate change is that for marginalized communities, climate change typically remains a few layers removed from the determinants of health. The community’s priorities may be at odds with a research and action agenda framed in terms of climate change and health
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