237 research outputs found

    Electrodynamics and energy characteristics of aurora at high resolution by optical methods

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    Technological advances leading to improved sensitivity of optical detectors have revealed that aurora contains a richness of dynamic and thin filamentary structures, but the source of the structured emissions is not fully understood. In addition, high resolution radar data have indicated that thin auroral arcs can be correlated with highly varying and large electric fields, but the detailed picture of the electrodynamics of auroral filaments is yet incomplete. The ASK instrument is a state-of-the-art ground-based instrument designed to investigate these smallest auroral features at very high spatial and temporal resolution, by using three EMCCDs in parallel for three different narrow spectral regions. ASK is specifically designed to utilize a new optical techique to determine the ionospheric electric fields. By imaging the long-lived O+ line at 732~nm, the plasma flow in the region can be traced, and since the plasma motion is controlled by the electric field, the field strength and direction can be estimated at unprecedented resolution. The method is a powerful tool to investigate the detailed electrodynamics and current systems around the thin auroral filaments. The two other ASK cameras provide information on the precipitation by imaging prompt emissions, and the emission brightness ratio of the two emissions, together with ion chemistry modeling, is used to give information on the energy and energy flux of the precipitating electrons. In this paper, we discuss these measuring techniques, and give a few examples of how they are used to reveal the nature and source of fine scale structuring in the auror

    Ecological risk assessment of invertebrates caught in Swedish west-coast fisheries

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    Ecological risk assessments are important as scientific support for the implementation of ecosystem-based fisheries management. Marine invertebrates are important to ecosystem structure and function and may be sensitive to fishing pressure. Some are also of increasing commercial value ā€“ but have hitherto not been paid much attention to in ecological risk assessments. Here, catches of invertebrates in Swedish west-coast fisheries with demersal trawls and creels are examined from an ecological risk assessment perspective. It is found that few non-commercial invertebrate species have been regularly recorded in onboard observer programs. Furthermore, for being a comparatively well-studied area, it is striking to find that out of the 93 species included, 56% could be classified as data deficient in terms of known attributes needed to perform basic ecological risk assessments. This implies that there is little or no available information on the basic life history traits important for estimating productivity. Additionally, onboard observer data for invertebrates are inadequate beyond targeted commercial species for robust statistical analysis on volumes generated over time and between fisheries. However, over 18% of the studied species are categorized as red-listed on the Swedish IUCN Red List. Combined with the few records available in observer data programs, the study illustrates the need to pay more attention to marine invertebrates in fisheries monitoring programs and research, especially bycaught and non-commercial invertebrate species

    Neutrophil Secretion Induced by an Intracellular Ca(2+) Rise and Followed by Whole-Cell Patch-Clamp Recordings Occurs Without any Selective Mobilization of Different Granule Populations

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    We have investigated calcium-induced secretion in human neutrophils, using a whole-cell patch-clamp technique. Mobilization of subcellular granules to the cell membrane was followed as the change in membrane capacitance (Ī”C(m)). Both the magnitude and the kinetics of the response differed between low and high concentrations of Ca(2+). A sustained secretion following a short lag phase was induced by high concentrations of Ca(2+) (100 Ī¼M and higher). A stable plateau was reached after 5ā€“7 minutes at Ī”C(m) values corresponding to values expected after all specific as well as azurophil granules have been mobilized. Capacitance values of the same magnitude could be obtained also at lower Ca(2+) concentrations, but typically no stable plateau was reached within the measuring time. In contrast to previous studies, we were unable to detect any pattern of secretion corresponding to a distinct submaximal response or selective mobilization of granule subsets specified by their Ca(2+)-sensitivity

    Compound auroral micromorphology: ground-based high-speed imaging

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    Auroral microphysics still remains partly unexplored. Cutting-edge ground-based optical observations using scientific complementary metal-oxide semiconductor (sCMOS) cameras recently enabled us to observe the fine-scale morphology of bright aurora at magnetic zenith for a variety of rapidly varying features for long uninterrupted periods. We report two interesting examples of combinations of fine-scale rapidly varying auroral features as observed by the sCMOS cameras installed at Poker Flat Research Range (PFRR), Alaska, in February 2014. The first example shows that flickering rays and pulsating modulation simultaneously appeared at the middle of a surge in the pre-midnight sector. The second example shows localized flickering aurora associated with growing eddies at the poleward edge of an arc in the midnight secto

    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

    ā€˜We need to get together and make ourselves heardā€™: 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 ā€˜non-politicalā€™ discussion forums ā€“ online lifestyle communities ā€“ 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 (2010ā€“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 ā€“ through talk ā€“ 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

    COMPOSE-HPC: A Transformational Approach to Exascale

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    The goal of the COMPOSE-HPC project is to 'democratize' tools for automatic transformation of program source code so that it becomes tractable for the developers of scientific applications to create and use their own transformations reliably and safely. This paper describes our approach to this challenge, the creation of the KNOT tool chain, which includes tools for the creation of annotation languages to control the transformations (PAUL), to perform the transformations (ROTE), and optimization and code generation (BRAID), which can be used individually and in combination. We also provide examples of current and future uses of the KNOT tools, which include transforming code to use different programming models and environments, providing tests that can be used to detect errors in software or its execution, as well as composition of software written in different programming languages, or with different threading patterns
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