2,191 research outputs found

    A dispersive wave pattern on Jupiter's fastest retrograde jet at 20∘20^\circS

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    A compact wave pattern has been identified on Jupiter's fastest retrograding jet at 20S (the SEBs) on the southern edge of the South Equatorial Belt. The wave has been identified in both reflected sunlight from amateur observations between 2010 and 2015, thermal infrared imaging from the Very Large Telescope and near infrared imaging from the Infrared Telescope Facility. The wave pattern is present when the SEB is relatively quiescent and lacking large-scale disturbances, and is particularly notable when the belt has undergone a fade (whitening). It is generally not present when the SEB exhibits its usual large-scale convective activity ('rifts'). Tracking of the wave pattern and associated white ovals on its southern edge over several epochs have permitted a measure of the dispersion relationship, showing a strong correlation between the phase speed (-43.2 to -21.2 m/s) and the longitudinal wavelength, which varied from 4.4-10.0 deg. longitude over the course of the observations. Infrared imaging sensing low pressures in the upper troposphere suggest that the wave is confined to near the cloud tops. The wave is moving westward at a phase speed slower (i.e., less negative) than the peak retrograde wind speed (-62 m/s), and is therefore moving east with respect to the SEBs jet peak. Unlike the retrograde NEBn jet near 17N, which is a location of strong vertical wind shear that sometimes hosts Rossby wave activity, the SEBs jet remains retrograde throughout the upper troposphere, suggesting the SEBs pattern cannot be interpreted as a classical Rossby wave. Cassini-derived windspeeds and temperatures reveal that the vorticity gradient is dominated by the baroclinic term and becomes negative (changes sign) in a region near the cloud-top level (400-700 mbar) associated with the SEBs, suggesting a baroclinic origin for this meandering wave pattern. [Abr]Comment: 19 pages, 11 figures, article accepted for publication in Icaru

    Investigating intra-host and intra-herd sequence diversity of foot-and-mouth disease virus

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    Due to the poor-fidelity of the enzymes involved in RNA genome replication, foot-and-mouth disease (FMD) virus samples comprise of unique polymorphic populations. In this study, deep sequencing was utilised to characterise the diversity of FMD virus (FMDV) populations in 6 infected cattle present on a single farm during the series of outbreaks in the UK in 2007. A novel RT–PCR method was developed to amplify a 7.6 kb nucleotide fragment encompassing the polyprotein coding region of the FMDV genome. Illumina sequencing of each sample identified the fine polymorphic structures at each nucleotide position, from consensus level changes to variants present at a 0.24% frequency. These data were used to investigate population dynamics of FMDV at both herd and host levels, evaluate the impact of host on the viral swarm structure and to identify transmission links with viruses recovered from other farms in the same series of outbreaks. In 7 samples, from 6 different animals, a total of 5 consensus level variants were identified, in addition to 104 sub-consensus variants of which 22 were shared between 2 or more animals. Further analysis revealed differences in swarm structures from samples derived from the same animal suggesting the presence of distinct viral populations evolving independently at different lesion sites within the same infected animal

    Neptune at Summer Solstice: Zonal Mean Temperatures from Ground-Based Observations 2003-2007

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    Imaging and spectroscopy of Neptune's thermal infrared emission is used to assess seasonal changes in Neptune's zonal mean temperatures between Voyager-2 observations (1989, heliocentric longitude Ls=236) and southern summer solstice (2005, Ls=270). Our aim was to analyse imaging and spectroscopy from multiple different sources using a single self-consistent radiative-transfer model to assess the magnitude of seasonal variability. Globally-averaged stratospheric temperatures measured from methane emission tend towards a quasi-isothermal structure (158-164 K) above the 0.1-mbar level, and are found to be consistent with spacecraft observations of AKARI. This remarkable consistency, despite very different observing conditions, suggests that stratospheric temporal variability, if present, is ±\pm5 K at 1 mbar and ±\pm3 K at 0.1 mbar during this solstice period. Conversely, ethane emission is highly variable, with abundance determinations varying by more than a factor of two. The retrieved C2H6 abundances are extremely sensitive to the details of the T(p) derivation. Stratospheric temperatures and ethane are found to be latitudinally uniform away from the south pole (assuming a latitudinally-uniform distribution of stratospheric methane). At low and midlatitudes, comparisons of synthetic Voyager-era images with solstice-era observations suggest that tropospheric zonal temperatures are unchanged since the Voyager 2 encounter, with cool mid-latitudes and a warm equator and pole. A re-analysis of Voyager/IRIS 25-50 {\mu}m mapping of tropospheric temperatures and para-hydrogen disequilibrium suggests a symmetric meridional circulation with cold air rising at mid-latitudes (sub-equilibrium para-H2 conditions) and warm air sinking at the equator and poles (super-equilibrium para-H2 conditions). The most significant atmospheric changes are associated with the polar vortex (absent in 1989).Comment: 35 pages, 19 figures. Accepted for publication in Icaru

    Cassini atmospheric chemistry mapper. Volume 1. Investigation and technical plan

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    The Cassini Atmospheric Chemistry Mapper (ACM) enables a broad range of atmospheric science investigations for Saturn and Titan by providing high spectral and spatial resolution mapping and occultation capabilities at 3 and 5 microns. ACM can directly address the major atmospheric science objectives for Saturn and for Titan, as defined by the Announcement of Opportunity, with pivotal diagnostic measurements not accessible to any other proposed Cassini instrument. ACM determines mixing ratios for atmospheric molecules from spectral line profiles for an important and extensive volume of the atmosphere of Saturn (and Jupiter). Spatial and vertical profiles of disequilibrium species abundances define Saturn's deep atmosphere, its chemistry, and its vertical transport phenomena. ACM spectral maps provide a unique means to interpret atmospheric conditions in the deep (approximately 1000 bar) atmosphere of Saturn. Deep chemistry and vertical transport is inferred from the vertical and horizontal distribution of a series of disequilibrium species. Solar occultations provide a method to bridge the altitude range in Saturn's (and Titan's) atmosphere that is not accessible to radio science, thermal infrared, and UV spectroscopy with temperature measurements to plus or minus 2K from the analysis of molecular line ratios and to attain an high sensitivity for low-abundance chemical species in the very large column densities that may be achieved during occultations for Saturn. For Titan, ACM solar occultations yield very well resolved (1/6 scale height) vertical mixing ratios column abundances for atmospheric molecular constituents. Occultations also provide for detecting abundant species very high in the upper atmosphere, while at greater depths, detecting the isotopes of C and O, constraining the production mechanisms, and/or sources for the above species. ACM measures the vertical and horizontal distribution of aerosols via their opacity at 3 microns and, particularly, at 5 microns. ACM recovers spatially-resolved atmospheric temperatures in Titan's troposphere via 3- and 5-microns spectral transitions. Together, the mixing ratio profiles and the aerosol distributions are utilized to investigate the photochemistry of the stratosphere and consequent formation processes for aerosols. Finally, ring opacities, observed during solar occultations and in reflected sunlight, provide a measurement of the particle size and distribution of ring material. ACM will be the first high spectral resolution mapping spectrometer on an outer planet mission for atmospheric studies while retaining a high resolution spatial mapping capability. ACM, thus, opens an entirely new range of orbital scientific studies of the origin, physio-chemical evolution and structure of the Saturn and Titan atmospheres. ACM provides high angular resolution spectral maps, viewing nadir and near-limb thermal radiation and reflected sunlight; sounds planetary limbs, spatially resolving vertical profiles to several atmospheric scale heights; and measures solar occultations, mapping both atmospheres and rings. ACM's high spectral and spatial resolution mapping capability is achieved with a simplified Fourier Transform spectrometer with a no-moving parts, physically compact design. ACM's simplicity guarantees an inherent stability essential for reliable performance throughout the lengthy Cassini Orbiter mission

    Evaluation of modelling approaches for predicting the spatial distribution of soil organic carbon stocks at the national scale

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    Soil organic carbon (SOC) plays a major role in the global carbon budget. It can act as a source or a sink of atmospheric carbon, thereby possibly influencing the course of climate change. Improving the tools that model the spatial distributions of SOC stocks at national scales is a priority, both for monitoring changes in SOC and as an input for global carbon cycles studies. In this paper, we compare and evaluate two recent and promising modelling approaches. First, we considered several increasingly complex boosted regression trees (BRT), a convenient and efficient multiple regression model from the statistical learning field. Further, we considered a robust geostatistical approach coupled to the BRT models. Testing the different approaches was performed on the dataset from the French Soil Monitoring Network, with a consistent cross-validation procedure. We showed that when a limited number of predictors were included in the BRT model, the standalone BRT predictions were significantly improved by robust geostatistical modelling of the residuals. However, when data for several SOC drivers were included, the standalone BRT model predictions were not significantly improved by geostatistical modelling. Therefore, in this latter situation, the BRT predictions might be considered adequate without the need for geostatistical modelling, provided that i) care is exercised in model fitting and validating, and ii) the dataset does not allow for modelling of local spatial autocorrelations, as is the case for many national systematic sampling schemes

    What is the impact on health and wellbeing of interventions that foster respect and social inclusion in community-residing older adults? A systematic review of quantitative and qualitative studies

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    Abstract Background Many interventions have been developed to promote respect and social inclusion among older people, but the evidence on their impacts on health has not been synthesised. This systematic review aims to appraise the state of the evidence across the quantitative and qualitative literature. Methods Eligible studies published between 1990 and 2015 were identified by scanning seven bibliographic databases using a pre-piloted strategy, searching grey literature and contacting experts. Studies were included if they assessed the impact (quantitatively) and/or perceived impact (qualitatively) of an intervention promoting respect and social inclusion on the physical or mental health of community-residing people aged 60 years and older. Titles and abstracts were screened for eligibility by one reviewer. A second reviewer independently screened a 10% random sample. Full texts were screened for eligibility by one reviewer, with verification by another reviewer. Risk of bias was assessed using standardised tools. Findings were summarised using narrative synthesis, harvest plots and logic models to depict the potential pathways to health outcomes. Results Of the 27,354 records retrieved, 40 studies (23 quantitative, 6 qualitative, 11 mixed methods) were included. All studies were conducted in high and upper middle-income countries. Interventions involved mentoring, intergenerational and multi-activity programmes, dancing, music and singing, art and culture and information-communication technology. Most studies (n = 24) were at high or moderate risk of bias. Music and singing, intergenerational interventions, art and culture and multi-activity interventions were associated with an overall positive impact on health outcomes. This included depression (n = 3), wellbeing (n = 3), subjective health (n = 2), quality of life (n = 2), perceived stress and mental health (n = 2) and physical health (n = 2). Qualitative studies offered explanations for mediating factors (e.g. improved self-esteem) that may lead to improved health outcomes and contributed to the assessment of causation. Conclusions Whilst this review suggests that some interventions may positively impact on the health outcomes of older people, and identified mediating factors to health outcomes, the evidence is based on studies with heterogeneous methodologies. Many of the interventions were delivered as projects to selected groups, raising important questions about the feasibility of wider implementation and the potential for population-wide benefits. Systematic review registration PROSPERO registration number CRD4201401010

    Maser Oscillation in a Whispering-Gallery-Mode Microwave Resonator

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    We report the first observation of above-threshold maser oscillation in a whispering-gallery(WG)-mode resonator, whose quasi-transverse-magnetic, 17th azimuthal-order WG mode, at a frequency of approx. 12.038 GHz, with a loaded Q of several hundred million, is supported on a cylinder of mono-crystalline sapphire. An electron spin resonance (ESR) associated with Fe3+ ions, that are substitutively included within the sapphire at a concentration of a few parts per billion, coincides in frequency with that of the (considerably narrower) WG mode. By applying a c.w. `pump' to the resonator at a frequency of approx. 31.34 GHz, with no applied d.c. magnetic field, the WG (`signal') mode is energized through a three-level maser scheme. Preliminary measurements demonstrate a frequency stability (Allan deviation) of a few times 1e-14 for sampling intervals up to 100 s.Comment: REVTeX v.4, 3 pages, with a separate .bbl file and 3 .eps figure

    Connecting Localism and Community Empowerment: Research Review and Critical Synthesis for the AHRC Connected Community Programme

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    The Connecting Localism and Community Empowerment project sought to assess the merits of the assumption that localisms brings about community empowerment through a review of the existing academic and policy literatures. The key findings from the review point towards a lack of clarity and coherence in the literature in the usage and interpretations of the terms ‗localism‘ and ‗community empowerment‘. They are often defined by implication or tacitly assumed to have an accepted definition. Whilst greater localism is generally claimed to increase community empowerment, there are substantive grounds for questioning this claim, which arise from critically analysing these concepts and how they interact. These grounds highlight conditions which need to be fulfilled if localism is to realise its potential to enhance community empowerment. To understand these conditions we analysed four international case studies. We also consider two assessments of the New Labour government‘s localist policies in the UK

    Comparison of Ion Mobility Spectrometry and Gas Chromatography with Dry Electrolytic Conductivity Detection for the Determination of Polychlorinated Biphenyls in Humus-Rich Soil

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    Ion mobility spectroscopy (IMS) has been showen to provide fast on-site analysis of coarse sandy soil for the determination of polychlorinated biphenyls (PCBs). However the presence of humus results in instrument foaling and extensive down time do to instrument clean-up. For this reason a method was investigated for the ultrasonic extraction of PCBs from humus-rich soil that could be used at remote locations. Analysis of the extracted PCBs was conducted using 1) IMS and 2) gas chromatogram equipped with a dry electolytic conductiviy detector (GC/DELCD). The research conducted for this thesis outlines the method development and analysis of PCBS using these two instruments. The IMS analyiss was found to be complicated by co-extracted matrix compounds. Results and limitations of IMS analysisare present here. The method development and validation of a method for the ultrasonic extraction and analysis of PCBs using the GC/DELCD is provided
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