1,910 research outputs found

    Photometry of Irregular Satellites of Uranus and Neptune

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    We present BVR photometric colors of six Uranian and two Neptunian irregular satellites, collected using the Magellan Observatory (Las Campanas, Chile) and the Keck Observatory, (Manua Kea, Hawaii). The colors range from neutral to light red, and like the Jovian and the Saturnian irregulars (Grav et al. 2003) there is an apparent lack of the extremely red objects found among the Centaurs and Kuiper belt objects. The Uranian irregulars can be divided into three possible dynamical families, but the colors collected show that two of these dynamical families, the Caliban and Sycorax-clusters, have heterogeneous colors. Of the third possible family, the 168-degree cluster containing two objects with similar average inclinations but quite different average semi-major axis, only one object (U XXI Trinculo) was observed. The heterogeneous colors and the large dispersion of the average orbital elements leads us to doubt that they are collisional families. We favor single captures as a more likely scenario. The two neptunians observed (N II Nereid and S/2002 N1) both have very similar neutral, sun-like colors. Together with the high collisional probability between these two objects over the age of the solar system (Nesvorny et al. 2003, Holman et al. 2004), this suggests that S/2002 N1 be a fragment of Nereid, broken loose during a collision or cratering event with an undetermined impactor.Comment: 13 pages (including 3 figures and 2 tables). Submitted to ApJ Letter

    Spectroscopy of D-type asteroids

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    We have performed a spectroscopic survey of 19 D-type asteroids. Comparison with previous photometry shows excellent agreement. Although the majority have similar colors to cometary nuclei, no cometary emission bands were present in any of the spectra. Absorption bands sporadically appearing were apparently due to stellar objects, and no features inherent to the asteroids were observed

    Campaigning and Contestation:Comments on politicians’ Facebook pages during the 2011 Danish general election campaign

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    This article is a critical study of the Facebook pages of politicians as public spheres using Dahlberg’s notion of contestation. A method is implemented inspired by qualitative content analysis and including focus groups in order to study citizen comments on eight main political candidates’ Facebook pages during the 2011 Danish election campaign. An analytical framework is presented that conceptualizes the particular platform as a dinner party, with a dinner table, a host, and the invited guests. The dinner party exhibits the interplay between these elements and how they limit the option of contesting the dominating discourse in favor of a supportive marketing logic

    ‘We need to get together and make ourselves heard’: everyday online spaces as incubators of political action

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    This article examines to what extent, and how, people engaging in political talk within ‘non-political’ discussion forums – online lifestyle communities – leads to political (or personal) action or calls-to-action. The analysis is framed in the context of wider questions of citizenship, civic engagement and political mobilization. To capture everyday political talk amongst citizens requires us to move beyond the now widely analysed online spaces of formal politics. Instead, we focus on online third spaces concerning lifestyle issues such as parenting, personal finance and popular culture. Drawing on a content analysis of three popular UK-based discussion forums over the course of five years (2010–2014), we found that (for two of the three cases) such spaces were more than just talking shops. Rather they were spaces where political actions not only emerged, but where they seemed to be cultivated. Discussions embedded in the personal lives of participants often developed – through talk – into political actions aimed at government (or other) authorities. The article sheds light on the contributing factors and processes that (potentially) trigger and foster action emerging from political talk and provides insight into the mobilization potential of third spaces

    Preferences of Hungarian consumers for quality, access and price attributes of health care services — result of a discrete choice experiment

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    In 2010, a household survey was carried out in Hungary among 1037 respondents to study consumer preferences and willingness to pay for health care services. In this paper, we use the data from the discrete choice experiments included in the survey, to elicit the preferences of health care consumers about the choice of health care providers. Regression analysis is used to estimate the effect of the improvement of service attributes (quality, access, and price) on patients’ choice, as well as the differences among the socio-demographic groups. We also estimate the marginal willingness to pay for the improvement in attribute levels by calculating marginal rates of substitution. The results show that respondents from a village or the capital, with low education and bad health status are more driven by the changes in the price attribute when choosing between health care providers. Respondents value the good skills and reputation of the physician and the attitude of the personnel most, followed by modern equipment and maintenance of the office/hospital. Access attributes (travelling and waiting time) are less important. The method of discrete choice experiment is useful to reveal patients’ preferences, and might support the development of an evidence-based and sustainable health policy on patient payments

    Tropical coastal habitats as surrogates of fish community structure, grazing, and fisheries value

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    Habitat maps are frequently invoked as surrogates of biodiversity to aid the design of networks of marine reserves. Maps are used to maximize habitat heterogeneity in reserves because this is likely to maximize the number of species protected. However, the technique's efficacy is limited by intra-habitat variability in the species present and their abundances. Although communities are expected to vary among patches of the same habitat, this variability is poorly documented and rarely incorporated into reserve planning. To examine intra-habitat variability in coral-reef fishes, we generated a data set from eight tropical coastal habitats and six islands in the Bahamian archipelago using underwater visual censuses. Firstly, we provide further support for habitat heterogeneity as a surrogate of biodiversity as each predefined habitat type supported a distinct assemblage of fishes. Intrahabitat variability in fish community structure at scales of hundreds of kilometers (among islands) was significant in at least 75% of the habitats studied, depending on whether presence/absence, density, or biomass data were used. Intra-habitat variability was positively correlated with the mean number of species in that habitat when density and biomass data were used. Such relationships provide a proxy for the assessment of intra-habitat variability when detailed quantitative data are scarce. Intra-habitat variability was examined in more detail for one habitat (forereefs visually dominated by Montastraea corals). Variability in community structure among islands was driven by small, demersal families (e. g., territorial pomacentrid and labrid fishes). Finally, we examined the ecological and economic significance of intra-habitat variability in fish assemblages on Montastraea reefs by identifying how this variability affects the composition and abundances of fishes in different functional groups, the key ecosystem process of parrotfish grazing, and the ecosystem service of value of commercially important finfish. There were significant differences in a range of functional groups and grazing, but not fisheries value. Variability at the scale of tens of kilometers (among reefs around an island) was less than that among islands. Caribbean marine reserves should be replicated at scales of hundreds of kilometers, particularly for species-rich habitats, to capture important intra-habitat variability in community structure, function, and an ecosystem process

    Decision for reconstructive interventions of the upper limb in individuals with tetraplegia: the effect of treatment characteristics

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    Objective: To determine the effect of treatment characteristics on the\ud decision for reconstructive interventions for the upper extremities (UE) in\ud subjects with tetraplegia. - \ud Setting: Seven specialized spinal cord injury centres in the Netherlands. - \ud Method: Treatment characteristics for UE reconstructive interventions were\ud determined. Conjoint analysis (CA) was used to determine the contribution\ud and the relative importance of the treatment characteristics on the decision\ud for therapy. Therefore, a number of different treatment scenarios using these\ud characteristics were established. Different pairs of scenarios were presented\ud to subjects who were asked to choose the preferred scenario of each set. - \ud Results: forty nine subjects with tetraplegia with a stable C5, C6 or C7\ud lesion were selected. All treatment characteristics significantly influenced\ud the choice for treatment. Relative importance of treatment characteristics\ud were: intervention type (surgery or surgery with FES implant) 13%, number\ud of operations 15%, in patient rehabilitation period 22%, ambulant\ud rehabilitation period 9%, complication rate 15%, improvement of elbow\ud function 10%, improvement of hand function 15%. In deciding for therapy\ud 40% of the subjects focused on one characteristic. - \ud Conclusion: CA is applicable in Spinal Cord Injury medicine to study the\ud effect of health outcomes and non-health outcomes on the decision for\ud treatment. Non-health outcomes which relate to the intensity of treatment\ud are equally important or even more important than functional outcome in the\ud decision for reconstructive UE surgery in subjects with tetraplegia

    Structure and dynamics of the nightside poleward boundary: Sounding rocket and ground-based observations of auroral electron precipitation in a rayed curtain

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    The Cascades2 auroral sounding rocket provides a case study for comparing multipoint in situ ionospheric observations of a nightside auroral poleward boundary intensification with ground-based optical observations of the same event. Cascades2 was launched northward from Poker Flat Alaska on 20 March 2009 at 11:04 UT. The 13 min flight reached an apogee of 564 km over the northern coast of Alaska. The experiment included a five-payload array of in situ instrumentation, ground cameras at three different points under the trajectory, multiple ground magnetometers, the Poker Flat Incoherent Scatter Radar (PFISR) radar, and the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft in the magnetotail. The rays of the poleward boundary intensification (PBI) curtain have along-arc motions of 8.5 km/s and along-arc spacings of 16 km. Modulated maximum energy envelopes and energy fluxes of the associated electron precipitation correspond to this spatial structure of the visible rays. The electron precipitation is additionally modulated at a higher frequency, and velocity dispersion analysis of these 8 Hz signatures implies Alfvénic wave-particle acceleration of an ambient ionospheric electron source occurring a few hundred km above the observation point. These observations parameterize the curtain of Alfvénic activity above the PBI event, both in the dispersive ionosphere and in the magnetotail reconnection region. The along-arc variations in brightness correspond to variations in precipitating electron energy flux interpreted as an along-arc modulation of the maximum energy of the Alfvénic wave-particle acceleration process; this is a new interpretation of the formation of rayed structures in auroral curtains. We consider the various possible magnetospheric and ionospheric drivers for the control of the observed along-arc structuring and motions
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