326 research outputs found

    Current applications of hyperspectral remote sensing in the discrimination of Australian Eucalypt species

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    hyperspectral remote sensing provides detail on biophysical variables related to forest ecosystem processes useful for tracking and predicting structure and function of vegetation considerable potential of laboratory spectrometry and near-range work in the field to derive stress indicators and changes in cholorphyll content has been demonstrated that includes a range of studies conducted on unique Australian vegetation types

    You Can't Get Through Szekeres Wormholes - or - Regularity, Topology and Causality in Quasi-Spherical Szekeres Models

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    The spherically symmetric dust model of Lemaitre-Tolman can describe wormholes, but the causal communication between the two asymptotic regions through the neck is even less than in the vacuum (Schwarzschild-Kruskal-Szekeres) case. We investigate the anisotropic generalisation of the wormhole topology in the Szekeres model. The function E(r, p, q) describes the deviation from spherical symmetry if \partial_r E \neq 0, but this requires the mass to be increasing with radius, \partial_r M > 0, i.e. non-zero density. We investigate the geometrical relations between the mass dipole and the locii of apparent horizon and of shell-crossings. We present the various conditions that ensure physically reasonable quasi-spherical models, including a regular origin, regular maxima and minima in the spatial sections, and the absence of shell-crossings. We show that physically reasonable values of \partial_r E \neq 0 cannot compensate for the effects of \partial_r M > 0 in any direction, so that communication through the neck is still worse than the vacuum. We also show that a handle topology cannot be created by identifying hypersufaces in the two asymptotic regions on either side of a wormhole, unless a surface layer is allowed at the junction. This impossibility includes the Schwarzschild-Kruskal-Szekeres case.Comment: zip file with LaTeX text + 6 figures (.eps & .ps). 47 pages. Second replacement corrects some minor errors and typos. (First replacement prints better on US letter size paper.

    Instability of black hole formation under small pressure perturbations

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    We investigate here the spectrum of gravitational collapse endstates when arbitrarily small perfect fluid pressures are introduced in the classic black hole formation scenario as described by Oppenheimer, Snyder and Datt (OSD) [1]. This extends a previous result on tangential pressures [2] to the more physically realistic scenario of perfect fluid collapse. The existence of classes of pressure perturbations is shown explicitly, which has the property that injecting any smallest pressure changes the final fate of the dynamical collapse from a black hole to a naked singularity. It is therefore seen that any smallest neighborhood of the OSD model, in the space of initial data, contains collapse evolutions that go to a naked singularity outcome. This gives an intriguing insight on the nature of naked singularity formation in gravitational collapse.Comment: 7 pages, 1 figure, several modifications to match published version on GR

    Organisational barriers to the facilitation of overseas volunteering and training placements in the NHS

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    Background Undertaking a period of voluntary work or a professional placement overseas has long been a feature of medical training in the UK. There are now a number of high profile National Health Service (NHS) initiatives aimed at increasing access to such opportunities for staff at all levels. We present findings from a qualitative study involving a range of NHS staff and other stakeholders which explored barriers to participation in these activities. Methods A grounded theory methodology was drawn upon to conduct thematic based analysis. Our data included in-depth, semi-structured interviews with a range of returned volunteers, non-volunteers and other stakeholders (n=51) who were, or had been, employed by the NHS. Results There are significant barriers to placement and volunteering activity stemming from structural and organisational shortcomings within the NHS. Difficulties in filling clinical roles has a significant impact on the ability of staff to plan and undertake independent placements. There is currently no clearly defined pathway within the NHS by which the majority of grades can apply for, or organise, a period of overseas voluntary or professional placement activity. There were divergent views on the relevance and usefulness of overseas professional placements. Conclusions We argue that in the context of current UK policy initiatives aimed at facilitating overseas volunteer and professional placement activity, urgent attention needs to be given to the structural and organisational framework within which such initiatives will be required to work

    Dark clouds in co-creation, and their silver linings practical challenges we faced in a participatory project in a resource-constrained community in India, and how we overcame (some of) them

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    BACKGROUND: While any type of field-based research is challenging, building action-oriented, participatory research in resource-constrained settings can be even more so. OBJECTIVE: In this article, we aim to examine and provide insights into some of the practical challenges that were faced during the course of a participatory project based in two non-notified slums in Bangalore, India, aiming to build solutions to indoor air pollution from cooking on traditional cook stoves. METHODS: The article draws upon experiences of the authors as field researchers engaged in a community-based project that adopted an exploratory, iterative design to its planning and implementation, which involved community visits, semi-structured interviews, prioritization workshops, community forums, photo voice activities, chulha-building sessions and cooking trials. RESULTS: The main obstacles to field work were linked to fostering open, continued dialogue with the community, aimed at bridging the gap between the 'scientific' and the 'local' worlds. Language and cultural barriers led to a reliance on interpreters, which affected both the quality of the interaction as well as the relationship between the researchers and the community that was built out of that interaction. The transience in housing and location of members of the community also led to difficulties in following up on incomplete information. Furthermore, facilitating meaningful participation from the people within the context of restricted resources, differing priorities, and socio-cultural diversity was particularly challenging. These were further compounded by the constraints of time and finances brought on by the embeddedness of the project within institutional frameworks and conventional research requirements of a fixed, pre-planned and externally determined focus, timeline, activities and benchmarks for the project. CONCLUSIONS: This article calls for revisiting of scientific conventions and funding prerequisites, in order to create spaces that support flexible, emergent and adaptive field-based research projects which can respond effectively to the needs and priorities of the community
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